1 /* 2 * Copyright (c) 2003, 2011, 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 // SystemDictionary::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 and JVM_CONSTANT_String entries are present in 214 // the class file, but are not stored in memory as such until they are 215 // resolved. The entries are not resolved unless they are used because 216 // resolution is expensive. During class file parsing the entries are 217 // initially stored in memory as JVM_CONSTANT_ClassIndex and 218 // JVM_CONSTANT_StringIndex entries. These special CP entry types 219 // indicate that the JVM_CONSTANT_Class and JVM_CONSTANT_String entries 220 // have been parsed, but the index values in the entries have not been 221 // validated. After the entire constant pool has been parsed, the index 222 // values can be validated and then the entries are converted into 223 // JVM_CONSTANT_UnresolvedClass and JVM_CONSTANT_UnresolvedString 224 // entries. During this conversion process, the UTF8 values that are 225 // indirectly referenced by the JVM_CONSTANT_ClassIndex and 226 // JVM_CONSTANT_StringIndex entries are changed into Symbol*s and the 227 // entries are modified to refer to the Symbol*s. This optimization 228 // eliminates one level of indirection for those two CP entry types and 229 // gets the entries ready for verification. During class file parsing 230 // it is also possible for JVM_CONSTANT_UnresolvedString entries to be 231 // resolved into JVM_CONSTANT_String entries. Verification expects to 232 // find JVM_CONSTANT_UnresolvedClass and either JVM_CONSTANT_String or 233 // JVM_CONSTANT_UnresolvedString entries and not JVM_CONSTANT_Class 234 // entries. 235 // 236 // Now we can get back to the copying complication. When we copy 237 // entries from old_cp to merge_cp, we have to revert any 238 // JVM_CONSTANT_Class entries to JVM_CONSTANT_UnresolvedClass entries 239 // or verification will fail. 240 // 241 // It is important to explicitly state that the merging algorithm 242 // effectively unresolves JVM_CONSTANT_Class entries that were in the 243 // old_cp when they are changed into JVM_CONSTANT_UnresolvedClass 244 // entries in the merge_cp. This is done both to make verification 245 // happy and to avoid adding more brittleness between RedefineClasses 246 // and the constant pool cache. By allowing the constant pool cache 247 // implementation to (re)resolve JVM_CONSTANT_UnresolvedClass entries 248 // into JVM_CONSTANT_Class entries, we avoid having to embed knowledge 249 // about those algorithms in RedefineClasses. 250 // 251 // Appending unique entries from scratch_cp to merge_cp is straight 252 // forward for direct CP entries and most indirect CP entries. For the 253 // indirect CP entry type JVM_CONSTANT_NameAndType and for the double- 254 // indirect CP entry types, the presence of more than one piece of 255 // interesting data makes appending the entries more complicated. 256 // 257 // For the JVM_CONSTANT_{Double,Float,Integer,Long,Utf8} entry types, 258 // the entry is simply copied from scratch_cp to the end of merge_cp. 259 // If the index in scratch_cp is different than the destination index 260 // in merge_cp, then the change in index value is tracked. 261 // 262 // Note: the above discussion for the direct CP entries also applies 263 // to the JVM_CONSTANT_Unresolved{Class,String} entry types. 264 // 265 // For the JVM_CONSTANT_{Class,String} entry types, since there is only 266 // one data element at the end of the recursion, we know that we have 267 // either one or two unique entries. If the JVM_CONSTANT_Utf8 entry is 268 // unique then it is appended to merge_cp before the current entry. 269 // If the JVM_CONSTANT_Utf8 entry is not unique, then the current entry 270 // is updated to refer to the duplicate entry in merge_cp before it is 271 // appended to merge_cp. Again, any changes in index values are tracked 272 // as needed. 273 // 274 // Note: the above discussion for JVM_CONSTANT_{Class,String} entry 275 // types is theoretical. Since those entry types have already been 276 // optimized into JVM_CONSTANT_Unresolved{Class,String} entry types, 277 // they are handled as direct CP entries. 278 // 279 // For the JVM_CONSTANT_NameAndType entry type, since there are two 280 // data elements at the end of the recursions, we know that we have 281 // between one and three unique entries. Any unique JVM_CONSTANT_Utf8 282 // entries are appended to merge_cp before the current entry. For any 283 // JVM_CONSTANT_Utf8 entries that are not unique, the current entry is 284 // updated to refer to the duplicate entry in merge_cp before it is 285 // appended to merge_cp. Again, any changes in index values are tracked 286 // as needed. 287 // 288 // For the JVM_CONSTANT_{Fieldref,InterfaceMethodref,Methodref} entry 289 // types, since there are two indirect CP entries and three data 290 // elements at the end of the recursions, we know that we have between 291 // one and six unique entries. See the JVM_CONSTANT_Fieldref diagram 292 // above for an example of all six entries. The uniqueness algorithm 293 // for the JVM_CONSTANT_Class and JVM_CONSTANT_NameAndType entries is 294 // covered above. Any unique entries are appended to merge_cp before 295 // the current entry. For any entries that are not unique, the current 296 // entry is updated to refer to the duplicate entry in merge_cp before 297 // it is appended to merge_cp. Again, any changes in index values are 298 // tracked as needed. 299 // 300 // 301 // Other Details: 302 // 303 // Details for other parts of RedefineClasses need to be written. 304 // This is a placeholder section. 305 // 306 // 307 // Open Issues (in no particular order): 308 // 309 // - How do we serialize the RedefineClasses() API without deadlocking? 310 // 311 // - SystemDictionary::parse_stream() was called with a NULL protection 312 // domain since the initial version. This has been changed to pass 313 // the_class->protection_domain(). This change has been tested with 314 // all NSK tests and nothing broke, but what will adding it now break 315 // in ways that we don't test? 316 // 317 // - GenerateOopMap::rewrite_load_or_store() has a comment in its 318 // (indirect) use of the Relocator class that the max instruction 319 // size is 4 bytes. goto_w and jsr_w are 5 bytes and wide/iinc is 320 // 6 bytes. Perhaps Relocator only needs a 4 byte buffer to do 321 // what it does to the bytecodes. More investigation is needed. 322 // 323 // - java.lang.Object methods can be called on arrays. This is 324 // implemented via the arrayKlassOop vtable which we don't 325 // update. For example, if we redefine java.lang.Object.toString(), 326 // then the new version of the method will not be called for array 327 // objects. 328 // 329 // - How do we know if redefine_single_class() and the guts of 330 // instanceKlass are out of sync? I don't think this can be 331 // automated, but we should probably order the work in 332 // redefine_single_class() to match the order of field 333 // definitions in instanceKlass. We also need to add some 334 // comments about keeping things in sync. 335 // 336 // - set_new_constant_pool() is huge and we should consider refactoring 337 // it into smaller chunks of work. 338 // 339 // - The exception table update code in set_new_constant_pool() defines 340 // const values that are also defined in a local context elsewhere. 341 // The same literal values are also used in elsewhere. We need to 342 // coordinate a cleanup of these constants with Runtime. 343 // 344 345 class VM_RedefineClasses: public VM_Operation { 346 private: 347 // These static fields are needed by SystemDictionary::classes_do() 348 // facility and the adjust_cpool_cache_and_vtable() helper: 349 static objArrayOop _old_methods; 350 static objArrayOop _new_methods; 351 static methodOop* _matching_old_methods; 352 static methodOop* _matching_new_methods; 353 static methodOop* _deleted_methods; 354 static methodOop* _added_methods; 355 static int _matching_methods_length; 356 static int _deleted_methods_length; 357 static int _added_methods_length; 358 static klassOop _the_class_oop; 359 360 // The instance fields are used to pass information from 361 // doit_prologue() to doit() and doit_epilogue(). 362 jint _class_count; 363 const jvmtiClassDefinition *_class_defs; // ptr to _class_count defs 364 365 // This operation is used by both RedefineClasses and 366 // RetransformClasses. Indicate which. 367 JvmtiClassLoadKind _class_load_kind; 368 369 // _index_map_count is just an optimization for knowing if 370 // _index_map_p contains any entries. 371 int _index_map_count; 372 intArray * _index_map_p; 373 // ptr to _class_count scratch_classes 374 instanceKlassHandle * _scratch_classes; 375 jvmtiError _res; 376 377 // Performance measurement support. These timers do not cover all 378 // the work done for JVM/TI RedefineClasses() but they do cover 379 // the heavy lifting. 380 elapsedTimer _timer_rsc_phase1; 381 elapsedTimer _timer_rsc_phase2; 382 elapsedTimer _timer_vm_op_prologue; 383 384 // These routines are roughly in call order unless otherwise noted. 385 386 // Load the caller's new class definition(s) into _scratch_classes. 387 // Constant pool merging work is done here as needed. Also calls 388 // compare_and_normalize_class_versions() to verify the class 389 // definition(s). 390 jvmtiError load_new_class_versions(TRAPS); 391 392 // Verify that the caller provided class definition(s) that meet 393 // the restrictions of RedefineClasses. Normalize the order of 394 // overloaded methods as needed. 395 jvmtiError compare_and_normalize_class_versions( 396 instanceKlassHandle the_class, instanceKlassHandle scratch_class); 397 398 // Swap annotations[i] with annotations[j] 399 // Used by compare_and_normalize_class_versions() when normalizing 400 // overloaded methods or changing idnum as when adding or deleting methods. 401 void swap_all_method_annotations(int i, int j, instanceKlassHandle scratch_class); 402 403 // Figure out which new methods match old methods in name and signature, 404 // which methods have been added, and which are no longer present 405 void compute_added_deleted_matching_methods(); 406 407 // Change jmethodIDs to point to the new methods 408 void update_jmethod_ids(); 409 410 // In addition to marking methods as obsolete, this routine 411 // records which methods are EMCP (Equivalent Module Constant 412 // Pool) in the emcp_methods BitMap and returns the number of 413 // EMCP methods via emcp_method_count_p. This information is 414 // used when information about the previous version of the_class 415 // is squirreled away. 416 void check_methods_and_mark_as_obsolete(BitMap *emcp_methods, 417 int * emcp_method_count_p); 418 void transfer_old_native_function_registrations(instanceKlassHandle the_class); 419 420 // Unevolving classes may point to methods of the_class directly 421 // from their constant pool caches, itables, and/or vtables. We 422 // use the SystemDictionary::classes_do() facility and this helper 423 // to fix up these pointers. 424 static void adjust_cpool_cache_and_vtable(klassOop k_oop, oop loader, TRAPS); 425 426 // Install the redefinition of a class 427 void redefine_single_class(jclass the_jclass, 428 instanceKlassHandle scratch_class, TRAPS); 429 430 // Increment the classRedefinedCount field in the specific instanceKlass 431 // and in all direct and indirect subclasses. 432 void increment_class_counter(instanceKlass *ik, TRAPS); 433 434 // Support for constant pool merging (these routines are in alpha 435 // order): 436 void append_entry(constantPoolHandle scratch_cp, int scratch_i, 437 constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS); 438 int find_new_index(int old_index); 439 bool is_unresolved_class_mismatch(constantPoolHandle cp1, int index1, 440 constantPoolHandle cp2, int index2); 441 bool is_unresolved_string_mismatch(constantPoolHandle cp1, int index1, 442 constantPoolHandle cp2, int index2); 443 void map_index(constantPoolHandle scratch_cp, int old_index, int new_index); 444 bool merge_constant_pools(constantPoolHandle old_cp, 445 constantPoolHandle scratch_cp, constantPoolHandle *merge_cp_p, 446 int *merge_cp_length_p, TRAPS); 447 jvmtiError merge_cp_and_rewrite(instanceKlassHandle the_class, 448 instanceKlassHandle scratch_class, TRAPS); 449 u2 rewrite_cp_ref_in_annotation_data( 450 typeArrayHandle annotations_typeArray, int &byte_i_ref, 451 const char * trace_mesg, TRAPS); 452 bool rewrite_cp_refs(instanceKlassHandle scratch_class, TRAPS); 453 bool rewrite_cp_refs_in_annotation_struct( 454 typeArrayHandle class_annotations, int &byte_i_ref, TRAPS); 455 bool rewrite_cp_refs_in_annotations_typeArray( 456 typeArrayHandle annotations_typeArray, int &byte_i_ref, TRAPS); 457 bool rewrite_cp_refs_in_class_annotations( 458 instanceKlassHandle scratch_class, TRAPS); 459 bool rewrite_cp_refs_in_element_value( 460 typeArrayHandle class_annotations, int &byte_i_ref, TRAPS); 461 bool rewrite_cp_refs_in_fields_annotations( 462 instanceKlassHandle scratch_class, TRAPS); 463 void rewrite_cp_refs_in_method(methodHandle method, 464 methodHandle * new_method_p, TRAPS); 465 bool rewrite_cp_refs_in_methods(instanceKlassHandle scratch_class, TRAPS); 466 bool rewrite_cp_refs_in_methods_annotations( 467 instanceKlassHandle scratch_class, TRAPS); 468 bool rewrite_cp_refs_in_methods_default_annotations( 469 instanceKlassHandle scratch_class, TRAPS); 470 bool rewrite_cp_refs_in_methods_parameter_annotations( 471 instanceKlassHandle scratch_class, TRAPS); 472 void rewrite_cp_refs_in_stack_map_table(methodHandle method, TRAPS); 473 void rewrite_cp_refs_in_verification_type_info( 474 address& stackmap_addr_ref, address stackmap_end, u2 frame_i, 475 u1 frame_size, TRAPS); 476 void set_new_constant_pool(instanceKlassHandle scratch_class, 477 constantPoolHandle scratch_cp, int scratch_cp_length, bool shrink, TRAPS); 478 479 void flush_dependent_code(instanceKlassHandle k_h, TRAPS); 480 481 static void check_class(klassOop k_oop, oop initiating_loader, TRAPS) PRODUCT_RETURN; 482 483 static void dump_methods() PRODUCT_RETURN; 484 485 public: 486 VM_RedefineClasses(jint class_count, 487 const jvmtiClassDefinition *class_defs, 488 JvmtiClassLoadKind class_load_kind); 489 VMOp_Type type() const { return VMOp_RedefineClasses; } 490 bool doit_prologue(); 491 void doit(); 492 void doit_epilogue(); 493 494 bool allow_nested_vm_operations() const { return true; } 495 jvmtiError check_error() { return _res; } 496 497 // Modifiable test must be shared between IsModifiableClass query 498 // and redefine implementation 499 static bool is_modifiable_class(oop klass_mirror); 500 }; 501 502 #endif // SHARE_VM_PRIMS_JVMTIREDEFINECLASSES_HPP