1 /* 2 * Copyright (c) 2003, 2013, 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 #ifndef SHARE_VM_PRIMS_JVMTIREDEFINECLASSES_HPP 26 #define SHARE_VM_PRIMS_JVMTIREDEFINECLASSES_HPP 27 28 #include "jvmtifiles/jvmtiEnv.hpp" 29 #include "memory/oopFactory.hpp" 30 #include "memory/resourceArea.hpp" 31 #include "oops/objArrayKlass.hpp" 32 #include "oops/objArrayOop.hpp" 33 #include "prims/jvmtiRedefineClassesTrace.hpp" 34 #include "runtime/vm_operations.hpp" 35 36 // Introduction: 37 // 38 // The RedefineClasses() API is used to change the definition of one or 39 // more classes. While the API supports redefining more than one class 40 // in a single call, in general, the API is discussed in the context of 41 // changing the definition of a single current class to a single new 42 // class. For clarity, the current class is will always be called 43 // "the_class" and the new class will always be called "scratch_class". 44 // 45 // The name "the_class" is used because there is only one structure 46 // that represents a specific class; redefinition does not replace the 47 // structure, but instead replaces parts of the structure. The name 48 // "scratch_class" is used because the structure that represents the 49 // new definition of a specific class is simply used to carry around 50 // the parts of the new definition until they are used to replace the 51 // appropriate parts in the_class. Once redefinition of a class is 52 // complete, scratch_class is thrown away. 53 // 54 // 55 // Implementation Overview: 56 // 57 // The RedefineClasses() API is mostly a wrapper around the VM op that 58 // does the real work. The work is split in varying degrees between 59 // doit_prologue(), doit() and doit_epilogue(). 60 // 61 // 1) doit_prologue() is called by the JavaThread on the way to a 62 // safepoint. It does parameter verification and loads scratch_class 63 // which involves: 64 // - parsing the incoming class definition using the_class' class 65 // loader and security context 66 // - linking scratch_class 67 // - merging constant pools and rewriting bytecodes as needed 68 // for the merged constant pool 69 // - verifying the bytecodes in scratch_class 70 // - setting up the constant pool cache and rewriting bytecodes 71 // as needed to use the cache 72 // - finally, scratch_class is compared to the_class to verify 73 // that it is a valid replacement class 74 // - if everything is good, then scratch_class is saved in an 75 // instance field in the VM operation for the doit() call 76 // 77 // Note: A JavaThread must do the above work. 78 // 79 // 2) doit() is called by the VMThread during a safepoint. It installs 80 // the new class definition(s) which involves: 81 // - retrieving the scratch_class from the instance field in the 82 // VM operation 83 // - house keeping (flushing breakpoints and caches, deoptimizing 84 // dependent compiled code) 85 // - replacing parts in the_class with parts from scratch_class 86 // - adding weak reference(s) to track the obsolete but interesting 87 // parts of the_class 88 // - adjusting constant pool caches and vtables in other classes 89 // that refer to methods in the_class. These adjustments use the 90 // ClassLoaderDataGraph::classes_do() facility which only allows 91 // a helper method to be specified. The interesting parameters 92 // that we would like to pass to the helper method are saved in 93 // static global fields in the VM operation. 94 // - telling the SystemDictionary to notice our changes 95 // 96 // Note: the above work must be done by the VMThread to be safe. 97 // 98 // 3) doit_epilogue() is called by the JavaThread after the VM op 99 // is finished and the safepoint is done. It simply cleans up 100 // memory allocated in doit_prologue() and used in doit(). 101 // 102 // 103 // Constant Pool Details: 104 // 105 // When the_class is redefined, we cannot just replace the constant 106 // pool in the_class with the constant pool from scratch_class because 107 // that could confuse obsolete methods that may still be running. 108 // Instead, the constant pool from the_class, old_cp, is merged with 109 // the constant pool from scratch_class, scratch_cp. The resulting 110 // constant pool, merge_cp, replaces old_cp in the_class. 111 // 112 // The key part of any merging algorithm is the entry comparison 113 // function so we have to know the types of entries in a constant pool 114 // in order to merge two of them together. Constant pools can contain 115 // up to 12 different kinds of entries; the JVM_CONSTANT_Unicode entry 116 // is not presently used so we only have to worry about the other 11 117 // entry types. For the purposes of constant pool merging, it is 118 // helpful to know that the 11 entry types fall into 3 different 119 // subtypes: "direct", "indirect" and "double-indirect". 120 // 121 // Direct CP entries contain data and do not contain references to 122 // other CP entries. The following are direct CP entries: 123 // JVM_CONSTANT_{Double,Float,Integer,Long,Utf8} 124 // 125 // Indirect CP entries contain 1 or 2 references to a direct CP entry 126 // and no other data. The following are indirect CP entries: 127 // JVM_CONSTANT_{Class,NameAndType,String} 128 // 129 // Double-indirect CP entries contain two references to indirect CP 130 // entries and no other data. The following are double-indirect CP 131 // entries: 132 // JVM_CONSTANT_{Fieldref,InterfaceMethodref,Methodref} 133 // 134 // When comparing entries between two constant pools, the entry types 135 // are compared first and if they match, then further comparisons are 136 // made depending on the entry subtype. Comparing direct CP entries is 137 // simply a matter of comparing the data associated with each entry. 138 // Comparing both indirect and double-indirect CP entries requires 139 // recursion. 140 // 141 // Fortunately, the recursive combinations are limited because indirect 142 // CP entries can only refer to direct CP entries and double-indirect 143 // CP entries can only refer to indirect CP entries. The following is 144 // an example illustration of the deepest set of indirections needed to 145 // access the data associated with a JVM_CONSTANT_Fieldref entry: 146 // 147 // JVM_CONSTANT_Fieldref { 148 // class_index => JVM_CONSTANT_Class { 149 // name_index => JVM_CONSTANT_Utf8 { 150 // <data-1> 151 // } 152 // } 153 // name_and_type_index => JVM_CONSTANT_NameAndType { 154 // name_index => JVM_CONSTANT_Utf8 { 155 // <data-2> 156 // } 157 // descriptor_index => JVM_CONSTANT_Utf8 { 158 // <data-3> 159 // } 160 // } 161 // } 162 // 163 // The above illustration is not a data structure definition for any 164 // computer language. The curly braces ('{' and '}') are meant to 165 // delimit the context of the "fields" in the CP entry types shown. 166 // Each indirection from the JVM_CONSTANT_Fieldref entry is shown via 167 // "=>", e.g., the class_index is used to indirectly reference a 168 // JVM_CONSTANT_Class entry where the name_index is used to indirectly 169 // reference a JVM_CONSTANT_Utf8 entry which contains the interesting 170 // <data-1>. In order to understand a JVM_CONSTANT_Fieldref entry, we 171 // have to do a total of 5 indirections just to get to the CP entries 172 // that contain the interesting pieces of data and then we have to 173 // fetch the three pieces of data. This means we have to do a total of 174 // (5 + 3) * 2 == 16 dereferences to compare two JVM_CONSTANT_Fieldref 175 // entries. 176 // 177 // Here is the indirection, data and dereference count for each entry 178 // type: 179 // 180 // JVM_CONSTANT_Class 1 indir, 1 data, 2 derefs 181 // JVM_CONSTANT_Double 0 indir, 1 data, 1 deref 182 // JVM_CONSTANT_Fieldref 2 indir, 3 data, 8 derefs 183 // JVM_CONSTANT_Float 0 indir, 1 data, 1 deref 184 // JVM_CONSTANT_Integer 0 indir, 1 data, 1 deref 185 // JVM_CONSTANT_InterfaceMethodref 2 indir, 3 data, 8 derefs 186 // JVM_CONSTANT_Long 0 indir, 1 data, 1 deref 187 // JVM_CONSTANT_Methodref 2 indir, 3 data, 8 derefs 188 // JVM_CONSTANT_NameAndType 1 indir, 2 data, 4 derefs 189 // JVM_CONSTANT_String 1 indir, 1 data, 2 derefs 190 // JVM_CONSTANT_Utf8 0 indir, 1 data, 1 deref 191 // 192 // So different subtypes of CP entries require different amounts of 193 // work for a proper comparison. 194 // 195 // Now that we've talked about the different entry types and how to 196 // compare them we need to get back to merging. This is not a merge in 197 // the "sort -u" sense or even in the "sort" sense. When we merge two 198 // constant pools, we copy all the entries from old_cp to merge_cp, 199 // preserving entry order. Next we append all the unique entries from 200 // scratch_cp to merge_cp and we track the index changes from the 201 // location in scratch_cp to the possibly new location in merge_cp. 202 // When we are done, any obsolete code that is still running that 203 // uses old_cp should not be able to observe any difference if it 204 // were to use merge_cp. As for the new code in scratch_class, it is 205 // modified to use the appropriate index values in merge_cp before it 206 // is used to replace the code in the_class. 207 // 208 // There is one small complication in copying the entries from old_cp 209 // to merge_cp. Two of the CP entry types are special in that they are 210 // lazily resolved. Before explaining the copying complication, we need 211 // to digress into CP entry resolution. 212 // 213 // JVM_CONSTANT_Class entries are present in the class file, but are not 214 // stored in memory as such until they are resolved. The entries are not 215 // resolved unless they are used because resolution is expensive. During class 216 // file parsing the entries are initially stored in memory as 217 // JVM_CONSTANT_ClassIndex and JVM_CONSTANT_StringIndex entries. These special 218 // CP entry types indicate that the JVM_CONSTANT_Class and JVM_CONSTANT_String 219 // entries have been parsed, but the index values in the entries have not been 220 // validated. After the entire constant pool has been parsed, the index 221 // values can be validated and then the entries are converted into 222 // JVM_CONSTANT_UnresolvedClass and JVM_CONSTANT_String 223 // entries. During this conversion process, the UTF8 values that are 224 // indirectly referenced by the JVM_CONSTANT_ClassIndex and 225 // JVM_CONSTANT_StringIndex entries are changed into Symbol*s and the 226 // entries are modified to refer to the Symbol*s. This optimization 227 // eliminates one level of indirection for those two CP entry types and 228 // gets the entries ready for verification. Verification expects to 229 // find JVM_CONSTANT_UnresolvedClass but not JVM_CONSTANT_Class entries. 230 // 231 // Now we can get back to the copying complication. When we copy 232 // entries from old_cp to merge_cp, we have to revert any 233 // JVM_CONSTANT_Class entries to JVM_CONSTANT_UnresolvedClass entries 234 // or verification will fail. 235 // 236 // It is important to explicitly state that the merging algorithm 237 // effectively unresolves JVM_CONSTANT_Class entries that were in the 238 // old_cp when they are changed into JVM_CONSTANT_UnresolvedClass 239 // entries in the merge_cp. This is done both to make verification 240 // happy and to avoid adding more brittleness between RedefineClasses 241 // and the constant pool cache. By allowing the constant pool cache 242 // implementation to (re)resolve JVM_CONSTANT_UnresolvedClass entries 243 // into JVM_CONSTANT_Class entries, we avoid having to embed knowledge 244 // about those algorithms in RedefineClasses. 245 // 246 // Appending unique entries from scratch_cp to merge_cp is straight 247 // forward for direct CP entries and most indirect CP entries. For the 248 // indirect CP entry type JVM_CONSTANT_NameAndType and for the double- 249 // indirect CP entry types, the presence of more than one piece of 250 // interesting data makes appending the entries more complicated. 251 // 252 // For the JVM_CONSTANT_{Double,Float,Integer,Long,Utf8} entry types, 253 // the entry is simply copied from scratch_cp to the end of merge_cp. 254 // If the index in scratch_cp is different than the destination index 255 // in merge_cp, then the change in index value is tracked. 256 // 257 // Note: the above discussion for the direct CP entries also applies 258 // to the JVM_CONSTANT_UnresolvedClass entry types. 259 // 260 // For the JVM_CONSTANT_Class entry types, since there is only 261 // one data element at the end of the recursion, we know that we have 262 // either one or two unique entries. If the JVM_CONSTANT_Utf8 entry is 263 // unique then it is appended to merge_cp before the current entry. 264 // If the JVM_CONSTANT_Utf8 entry is not unique, then the current entry 265 // is updated to refer to the duplicate entry in merge_cp before it is 266 // appended to merge_cp. Again, any changes in index values are tracked 267 // as needed. 268 // 269 // Note: the above discussion for JVM_CONSTANT_Class entry 270 // types is theoretical. Since those entry types have already been 271 // optimized into JVM_CONSTANT_UnresolvedClass entry types, 272 // they are handled as direct CP entries. 273 // 274 // For the JVM_CONSTANT_NameAndType entry type, since there are two 275 // data elements at the end of the recursions, we know that we have 276 // between one and three unique entries. Any unique JVM_CONSTANT_Utf8 277 // entries are appended to merge_cp before the current entry. For any 278 // JVM_CONSTANT_Utf8 entries that are not unique, the current entry is 279 // updated to refer to the duplicate entry in merge_cp before it is 280 // appended to merge_cp. Again, any changes in index values are tracked 281 // as needed. 282 // 283 // For the JVM_CONSTANT_{Fieldref,InterfaceMethodref,Methodref} entry 284 // types, since there are two indirect CP entries and three data 285 // elements at the end of the recursions, we know that we have between 286 // one and six unique entries. See the JVM_CONSTANT_Fieldref diagram 287 // above for an example of all six entries. The uniqueness algorithm 288 // for the JVM_CONSTANT_Class and JVM_CONSTANT_NameAndType entries is 289 // covered above. Any unique entries are appended to merge_cp before 290 // the current entry. For any entries that are not unique, the current 291 // entry is updated to refer to the duplicate entry in merge_cp before 292 // it is appended to merge_cp. Again, any changes in index values are 293 // tracked as needed. 294 // 295 // 296 // Other Details: 297 // 298 // Details for other parts of RedefineClasses need to be written. 299 // This is a placeholder section. 300 // 301 // 302 // Open Issues (in no particular order): 303 // 304 // - How do we serialize the RedefineClasses() API without deadlocking? 305 // 306 // - SystemDictionary::parse_stream() was called with a NULL protection 307 // domain since the initial version. This has been changed to pass 308 // the_class->protection_domain(). This change has been tested with 309 // all NSK tests and nothing broke, but what will adding it now break 310 // in ways that we don't test? 311 // 312 // - GenerateOopMap::rewrite_load_or_store() has a comment in its 313 // (indirect) use of the Relocator class that the max instruction 314 // size is 4 bytes. goto_w and jsr_w are 5 bytes and wide/iinc is 315 // 6 bytes. Perhaps Relocator only needs a 4 byte buffer to do 316 // what it does to the bytecodes. More investigation is needed. 317 // 318 // - How do we know if redefine_single_class() and the guts of 319 // InstanceKlass are out of sync? I don't think this can be 320 // automated, but we should probably order the work in 321 // redefine_single_class() to match the order of field 322 // definitions in InstanceKlass. We also need to add some 323 // comments about keeping things in sync. 324 // 325 // - set_new_constant_pool() is huge and we should consider refactoring 326 // it into smaller chunks of work. 327 // 328 // - The exception table update code in set_new_constant_pool() defines 329 // const values that are also defined in a local context elsewhere. 330 // The same literal values are also used in elsewhere. We need to 331 // coordinate a cleanup of these constants with Runtime. 332 // 333 334 struct JvmtiCachedClassFileData { 335 jint length; 336 unsigned char data[1]; 337 }; 338 339 class VM_RedefineClasses: public VM_Operation { 340 private: 341 // These static fields are needed by ClassLoaderDataGraph::classes_do() 342 // facility and the AdjustCpoolCacheAndVtable helper: 343 static Array<Method*>* _old_methods; 344 static Array<Method*>* _new_methods; 345 static Method** _matching_old_methods; 346 static Method** _matching_new_methods; 347 static Method** _deleted_methods; 348 static Method** _added_methods; 349 static int _matching_methods_length; 350 static int _deleted_methods_length; 351 static int _added_methods_length; 352 static Klass* _the_class_oop; 353 354 // The instance fields are used to pass information from 355 // doit_prologue() to doit() and doit_epilogue(). 356 jint _class_count; 357 const jvmtiClassDefinition *_class_defs; // ptr to _class_count defs 358 359 // This operation is used by both RedefineClasses and 360 // RetransformClasses. Indicate which. 361 JvmtiClassLoadKind _class_load_kind; 362 363 // _index_map_count is just an optimization for knowing if 364 // _index_map_p contains any entries. 365 int _index_map_count; 366 intArray * _index_map_p; 367 368 // _operands_index_map_count is just an optimization for knowing if 369 // _operands_index_map_p contains any entries. 370 int _operands_cur_length; 371 int _operands_index_map_count; 372 intArray * _operands_index_map_p; 373 374 // ptr to _class_count scratch_classes 375 Klass** _scratch_classes; 376 jvmtiError _res; 377 378 // Performance measurement support. These timers do not cover all 379 // the work done for JVM/TI RedefineClasses() but they do cover 380 // the heavy lifting. 381 elapsedTimer _timer_rsc_phase1; 382 elapsedTimer _timer_rsc_phase2; 383 elapsedTimer _timer_vm_op_prologue; 384 385 // These routines are roughly in call order unless otherwise noted. 386 387 // Load the caller's new class definition(s) into _scratch_classes. 388 // Constant pool merging work is done here as needed. Also calls 389 // compare_and_normalize_class_versions() to verify the class 390 // definition(s). 391 jvmtiError load_new_class_versions(TRAPS); 392 393 // Verify that the caller provided class definition(s) that meet 394 // the restrictions of RedefineClasses. Normalize the order of 395 // overloaded methods as needed. 396 jvmtiError compare_and_normalize_class_versions( 397 instanceKlassHandle the_class, instanceKlassHandle scratch_class); 398 399 // Figure out which new methods match old methods in name and signature, 400 // which methods have been added, and which are no longer present 401 void compute_added_deleted_matching_methods(); 402 403 // Change jmethodIDs to point to the new methods 404 void update_jmethod_ids(); 405 406 // In addition to marking methods as obsolete, this routine 407 // records which methods are EMCP (Equivalent Module Constant 408 // Pool) in the emcp_methods BitMap and returns the number of 409 // EMCP methods via emcp_method_count_p. This information is 410 // used when information about the previous version of the_class 411 // is squirreled away. 412 void check_methods_and_mark_as_obsolete(BitMap *emcp_methods, 413 int * emcp_method_count_p); 414 void transfer_old_native_function_registrations(instanceKlassHandle the_class); 415 416 // Install the redefinition of a class 417 void redefine_single_class(jclass the_jclass, 418 Klass* scratch_class_oop, TRAPS); 419 420 void swap_annotations(instanceKlassHandle new_class, 421 instanceKlassHandle scratch_class); 422 423 // Increment the classRedefinedCount field in the specific InstanceKlass 424 // and in all direct and indirect subclasses. 425 void increment_class_counter(InstanceKlass *ik, TRAPS); 426 427 // Support for constant pool merging (these routines are in alpha order): 428 void append_entry(constantPoolHandle scratch_cp, int scratch_i, 429 constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS); 430 void append_operand(constantPoolHandle scratch_cp, int scratch_bootstrap_spec_index, 431 constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS); 432 void finalize_operands_merge(constantPoolHandle merge_cp, TRAPS); 433 int find_or_append_indirect_entry(constantPoolHandle scratch_cp, int scratch_i, 434 constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS); 435 int find_or_append_operand(constantPoolHandle scratch_cp, int scratch_bootstrap_spec_index, 436 constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS); 437 int find_new_index(int old_index); 438 int find_new_operand_index(int old_bootstrap_spec_index); 439 bool is_unresolved_class_mismatch(constantPoolHandle cp1, int index1, 440 constantPoolHandle cp2, int index2); 441 void map_index(constantPoolHandle scratch_cp, int old_index, int new_index); 442 void map_operand_index(int old_bootstrap_spec_index, int new_bootstrap_spec_index); 443 bool merge_constant_pools(constantPoolHandle old_cp, 444 constantPoolHandle scratch_cp, constantPoolHandle *merge_cp_p, 445 int *merge_cp_length_p, TRAPS); 446 jvmtiError merge_cp_and_rewrite(instanceKlassHandle the_class, 447 instanceKlassHandle scratch_class, TRAPS); 448 u2 rewrite_cp_ref_in_annotation_data( 449 AnnotationArray* annotations_typeArray, int &byte_i_ref, 450 const char * trace_mesg, TRAPS); 451 bool rewrite_cp_refs(instanceKlassHandle scratch_class, TRAPS); 452 bool rewrite_cp_refs_in_annotation_struct( 453 AnnotationArray* class_annotations, int &byte_i_ref, TRAPS); 454 bool rewrite_cp_refs_in_annotations_typeArray( 455 AnnotationArray* annotations_typeArray, int &byte_i_ref, TRAPS); 456 bool rewrite_cp_refs_in_class_annotations( 457 instanceKlassHandle scratch_class, TRAPS); 458 bool rewrite_cp_refs_in_element_value( 459 AnnotationArray* class_annotations, int &byte_i_ref, TRAPS); 460 bool rewrite_cp_refs_in_type_annotations_typeArray( 461 AnnotationArray* type_annotations_typeArray, int &byte_i_ref, 462 const char * location_mesg, TRAPS); 463 bool rewrite_cp_refs_in_type_annotation_struct( 464 AnnotationArray* type_annotations_typeArray, int &byte_i_ref, 465 const char * location_mesg, TRAPS); 466 bool skip_type_annotation_target( 467 AnnotationArray* type_annotations_typeArray, int &byte_i_ref, 468 const char * location_mesg, TRAPS); 469 bool skip_type_annotation_type_path( 470 AnnotationArray* type_annotations_typeArray, int &byte_i_ref, TRAPS); 471 bool rewrite_cp_refs_in_fields_annotations( 472 instanceKlassHandle scratch_class, TRAPS); 473 void rewrite_cp_refs_in_method(methodHandle method, 474 methodHandle * new_method_p, TRAPS); 475 bool rewrite_cp_refs_in_methods(instanceKlassHandle scratch_class, TRAPS); 476 bool rewrite_cp_refs_in_methods_annotations( 477 instanceKlassHandle scratch_class, TRAPS); 478 bool rewrite_cp_refs_in_methods_default_annotations( 479 instanceKlassHandle scratch_class, TRAPS); 480 bool rewrite_cp_refs_in_methods_parameter_annotations( 481 instanceKlassHandle scratch_class, TRAPS); 482 bool rewrite_cp_refs_in_class_type_annotations( 483 instanceKlassHandle scratch_class, TRAPS); 484 bool rewrite_cp_refs_in_fields_type_annotations( 485 instanceKlassHandle scratch_class, TRAPS); 486 bool rewrite_cp_refs_in_methods_type_annotations( 487 instanceKlassHandle scratch_class, TRAPS); 488 void rewrite_cp_refs_in_stack_map_table(methodHandle method, TRAPS); 489 void rewrite_cp_refs_in_verification_type_info( 490 address& stackmap_addr_ref, address stackmap_end, u2 frame_i, 491 u1 frame_size, TRAPS); 492 void set_new_constant_pool(ClassLoaderData* loader_data, 493 instanceKlassHandle scratch_class, 494 constantPoolHandle scratch_cp, int scratch_cp_length, TRAPS); 495 496 void flush_dependent_code(instanceKlassHandle k_h, TRAPS); 497 498 static void dump_methods(); 499 500 // Check that there are no old or obsolete methods 501 class CheckClass : public KlassClosure { 502 Thread* _thread; 503 public: 504 CheckClass(Thread* t) : _thread(t) {} 505 void do_klass(Klass* k); 506 }; 507 508 // Unevolving classes may point to methods of the_class directly 509 // from their constant pool caches, itables, and/or vtables. We 510 // use the ClassLoaderDataGraph::classes_do() facility and this helper 511 // to fix up these pointers. 512 class AdjustCpoolCacheAndVtable : public KlassClosure { 513 Thread* _thread; 514 public: 515 AdjustCpoolCacheAndVtable(Thread* t) : _thread(t) {} 516 void do_klass(Klass* k); 517 }; 518 519 public: 520 VM_RedefineClasses(jint class_count, 521 const jvmtiClassDefinition *class_defs, 522 JvmtiClassLoadKind class_load_kind); 523 VMOp_Type type() const { return VMOp_RedefineClasses; } 524 bool doit_prologue(); 525 void doit(); 526 void doit_epilogue(); 527 528 bool allow_nested_vm_operations() const { return true; } 529 jvmtiError check_error() { return _res; } 530 531 // Modifiable test must be shared between IsModifiableClass query 532 // and redefine implementation 533 static bool is_modifiable_class(oop klass_mirror); 534 535 static jint get_cached_class_file_len(JvmtiCachedClassFileData *cache) { 536 return cache == NULL ? 0 : cache->length; 537 } 538 static unsigned char * get_cached_class_file_bytes(JvmtiCachedClassFileData *cache) { 539 return cache == NULL ? NULL : cache->data; 540 } 541 }; 542 #endif // SHARE_VM_PRIMS_JVMTIREDEFINECLASSES_HPP