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  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