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+/*
+ * Copyright 2003-2006 Sun Microsystems, Inc.  All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+// Introduction:
+//
+// The RedefineClasses() API is used to change the definition of one or
+// more classes. While the API supports redefining more than one class
+// in a single call, in general, the API is discussed in the context of
+// changing the definition of a single current class to a single new
+// class. For clarity, the current class is will always be called
+// "the_class" and the new class will always be called "scratch_class".
+//
+// The name "the_class" is used because there is only one structure
+// that represents a specific class; redefinition does not replace the
+// structure, but instead replaces parts of the structure. The name
+// "scratch_class" is used because the structure that represents the
+// new definition of a specific class is simply used to carry around
+// the parts of the new definition until they are used to replace the
+// appropriate parts in the_class. Once redefinition of a class is
+// complete, scratch_class is thrown away.
+//
+//
+// Implementation Overview:
+//
+// The RedefineClasses() API is mostly a wrapper around the VM op that
+// does the real work. The work is split in varying degrees between
+// doit_prologue(), doit() and doit_epilogue().
+//
+// 1) doit_prologue() is called by the JavaThread on the way to a
+//    safepoint. It does parameter verification and loads scratch_class
+//    which involves:
+//    - parsing the incoming class definition using the_class' class
+//      loader and security context
+//    - linking scratch_class
+//    - merging constant pools and rewriting bytecodes as needed
+//      for the merged constant pool
+//    - verifying the bytecodes in scratch_class
+//    - setting up the constant pool cache and rewriting bytecodes
+//      as needed to use the cache
+//    - finally, scratch_class is compared to the_class to verify
+//      that it is a valid replacement class
+//    - if everything is good, then scratch_class is saved in an
+//      instance field in the VM operation for the doit() call
+//
+//    Note: A JavaThread must do the above work.
+//
+// 2) doit() is called by the VMThread during a safepoint. It installs
+//    the new class definition(s) which involves:
+//    - retrieving the scratch_class from the instance field in the
+//      VM operation
+//    - house keeping (flushing breakpoints and caches, deoptimizing
+//      dependent compiled code)
+//    - replacing parts in the_class with parts from scratch_class
+//    - adding weak reference(s) to track the obsolete but interesting
+//      parts of the_class
+//    - adjusting constant pool caches and vtables in other classes
+//      that refer to methods in the_class. These adjustments use the
+//      SystemDictionary::classes_do() facility which only allows
+//      a helper method to be specified. The interesting parameters
+//      that we would like to pass to the helper method are saved in
+//      static global fields in the VM operation.
+//    - telling the SystemDictionary to notice our changes
+//
+//    Note: the above work must be done by the VMThread to be safe.
+//
+// 3) doit_epilogue() is called by the JavaThread after the VM op
+//    is finished and the safepoint is done. It simply cleans up
+//    memory allocated in doit_prologue() and used in doit().
+//
+//
+// Constant Pool Details:
+//
+// When the_class is redefined, we cannot just replace the constant
+// pool in the_class with the constant pool from scratch_class because
+// that could confuse obsolete methods that may still be running.
+// Instead, the constant pool from the_class, old_cp, is merged with
+// the constant pool from scratch_class, scratch_cp. The resulting
+// constant pool, merge_cp, replaces old_cp in the_class.
+//
+// The key part of any merging algorithm is the entry comparison
+// function so we have to know the types of entries in a constant pool
+// in order to merge two of them together. Constant pools can contain
+// up to 12 different kinds of entries; the JVM_CONSTANT_Unicode entry
+// is not presently used so we only have to worry about the other 11
+// entry types. For the purposes of constant pool merging, it is
+// helpful to know that the 11 entry types fall into 3 different
+// subtypes: "direct", "indirect" and "double-indirect".
+//
+// Direct CP entries contain data and do not contain references to
+// other CP entries. The following are direct CP entries:
+//     JVM_CONSTANT_{Double,Float,Integer,Long,Utf8}
+//
+// Indirect CP entries contain 1 or 2 references to a direct CP entry
+// and no other data. The following are indirect CP entries:
+//     JVM_CONSTANT_{Class,NameAndType,String}
+//
+// Double-indirect CP entries contain two references to indirect CP
+// entries and no other data. The following are double-indirect CP
+// entries:
+//     JVM_CONSTANT_{Fieldref,InterfaceMethodref,Methodref}
+//
+// When comparing entries between two constant pools, the entry types
+// are compared first and if they match, then further comparisons are
+// made depending on the entry subtype. Comparing direct CP entries is
+// simply a matter of comparing the data associated with each entry.
+// Comparing both indirect and double-indirect CP entries requires
+// recursion.
+//
+// Fortunately, the recursive combinations are limited because indirect
+// CP entries can only refer to direct CP entries and double-indirect
+// CP entries can only refer to indirect CP entries. The following is
+// an example illustration of the deepest set of indirections needed to
+// access the data associated with a JVM_CONSTANT_Fieldref entry:
+//
+//     JVM_CONSTANT_Fieldref {
+//         class_index => JVM_CONSTANT_Class {
+//             name_index => JVM_CONSTANT_Utf8 {
+//                 <data-1>
+//             }
+//         }
+//         name_and_type_index => JVM_CONSTANT_NameAndType {
+//             name_index => JVM_CONSTANT_Utf8 {
+//                 <data-2>
+//             }
+//             descriptor_index => JVM_CONSTANT_Utf8 {
+//                 <data-3>
+//             }
+//         }
+//     }
+//
+// The above illustration is not a data structure definition for any
+// computer language. The curly braces ('{' and '}') are meant to
+// delimit the context of the "fields" in the CP entry types shown.
+// Each indirection from the JVM_CONSTANT_Fieldref entry is shown via
+// "=>", e.g., the class_index is used to indirectly reference a
+// JVM_CONSTANT_Class entry where the name_index is used to indirectly
+// reference a JVM_CONSTANT_Utf8 entry which contains the interesting
+// <data-1>. In order to understand a JVM_CONSTANT_Fieldref entry, we
+// have to do a total of 5 indirections just to get to the CP entries
+// that contain the interesting pieces of data and then we have to
+// fetch the three pieces of data. This means we have to do a total of
+// (5 + 3) * 2 == 16 dereferences to compare two JVM_CONSTANT_Fieldref
+// entries.
+//
+// Here is the indirection, data and dereference count for each entry
+// type:
+//
+//    JVM_CONSTANT_Class               1 indir, 1 data, 2 derefs
+//    JVM_CONSTANT_Double              0 indir, 1 data, 1 deref
+//    JVM_CONSTANT_Fieldref            2 indir, 3 data, 8 derefs
+//    JVM_CONSTANT_Float               0 indir, 1 data, 1 deref
+//    JVM_CONSTANT_Integer             0 indir, 1 data, 1 deref
+//    JVM_CONSTANT_InterfaceMethodref  2 indir, 3 data, 8 derefs
+//    JVM_CONSTANT_Long                0 indir, 1 data, 1 deref
+//    JVM_CONSTANT_Methodref           2 indir, 3 data, 8 derefs
+//    JVM_CONSTANT_NameAndType         1 indir, 2 data, 4 derefs
+//    JVM_CONSTANT_String              1 indir, 1 data, 2 derefs
+//    JVM_CONSTANT_Utf8                0 indir, 1 data, 1 deref
+//
+// So different subtypes of CP entries require different amounts of
+// work for a proper comparison.
+//
+// Now that we've talked about the different entry types and how to
+// compare them we need to get back to merging. This is not a merge in
+// the "sort -u" sense or even in the "sort" sense. When we merge two
+// constant pools, we copy all the entries from old_cp to merge_cp,
+// preserving entry order. Next we append all the unique entries from
+// scratch_cp to merge_cp and we track the index changes from the
+// location in scratch_cp to the possibly new location in merge_cp.
+// When we are done, any obsolete code that is still running that
+// uses old_cp should not be able to observe any difference if it
+// were to use merge_cp. As for the new code in scratch_class, it is
+// modified to use the appropriate index values in merge_cp before it
+// is used to replace the code in the_class.
+//
+// There is one small complication in copying the entries from old_cp
+// to merge_cp. Two of the CP entry types are special in that they are
+// lazily resolved. Before explaining the copying complication, we need
+// to digress into CP entry resolution.
+//
+// JVM_CONSTANT_Class and JVM_CONSTANT_String entries are present in
+// the class file, but are not stored in memory as such until they are
+// resolved. The entries are not resolved unless they are used because
+// resolution is expensive. During class file parsing the entries are
+// initially stored in memory as JVM_CONSTANT_ClassIndex and
+// JVM_CONSTANT_StringIndex entries. These special CP entry types
+// indicate that the JVM_CONSTANT_Class and JVM_CONSTANT_String entries
+// have been parsed, but the index values in the entries have not been
+// validated. After the entire constant pool has been parsed, the index
+// values can be validated and then the entries are converted into
+// JVM_CONSTANT_UnresolvedClass and JVM_CONSTANT_UnresolvedString
+// entries. During this conversion process, the UTF8 values that are
+// indirectly referenced by the JVM_CONSTANT_ClassIndex and
+// JVM_CONSTANT_StringIndex entries are changed into symbolOops and the
+// entries are modified to refer to the symbolOops. This optimization
+// eliminates one level of indirection for those two CP entry types and
+// gets the entries ready for verification. During class file parsing
+// it is also possible for JVM_CONSTANT_UnresolvedString entries to be
+// resolved into JVM_CONSTANT_String entries. Verification expects to
+// find JVM_CONSTANT_UnresolvedClass and either JVM_CONSTANT_String or
+// JVM_CONSTANT_UnresolvedString entries and not JVM_CONSTANT_Class
+// entries.
+//
+// Now we can get back to the copying complication. When we copy
+// entries from old_cp to merge_cp, we have to revert any
+// JVM_CONSTANT_Class entries to JVM_CONSTANT_UnresolvedClass entries
+// or verification will fail.
+//
+// It is important to explicitly state that the merging algorithm
+// effectively unresolves JVM_CONSTANT_Class entries that were in the
+// old_cp when they are changed into JVM_CONSTANT_UnresolvedClass
+// entries in the merge_cp. This is done both to make verification
+// happy and to avoid adding more brittleness between RedefineClasses
+// and the constant pool cache. By allowing the constant pool cache
+// implementation to (re)resolve JVM_CONSTANT_UnresolvedClass entries
+// into JVM_CONSTANT_Class entries, we avoid having to embed knowledge
+// about those algorithms in RedefineClasses.
+//
+// Appending unique entries from scratch_cp to merge_cp is straight
+// forward for direct CP entries and most indirect CP entries. For the
+// indirect CP entry type JVM_CONSTANT_NameAndType and for the double-
+// indirect CP entry types, the presence of more than one piece of
+// interesting data makes appending the entries more complicated.
+//
+// For the JVM_CONSTANT_{Double,Float,Integer,Long,Utf8} entry types,
+// the entry is simply copied from scratch_cp to the end of merge_cp.
+// If the index in scratch_cp is different than the destination index
+// in merge_cp, then the change in index value is tracked.
+//
+// Note: the above discussion for the direct CP entries also applies
+// to the JVM_CONSTANT_Unresolved{Class,String} entry types.
+//
+// For the JVM_CONSTANT_{Class,String} entry types, since there is only
+// one data element at the end of the recursion, we know that we have
+// either one or two unique entries. If the JVM_CONSTANT_Utf8 entry is
+// unique then it is appended to merge_cp before the current entry.
+// If the JVM_CONSTANT_Utf8 entry is not unique, then the current entry
+// is updated to refer to the duplicate entry in merge_cp before it is
+// appended to merge_cp. Again, any changes in index values are tracked
+// as needed.
+//
+// Note: the above discussion for JVM_CONSTANT_{Class,String} entry
+// types is theoretical. Since those entry types have already been
+// optimized into JVM_CONSTANT_Unresolved{Class,String} entry types,
+// they are handled as direct CP entries.
+//
+// For the JVM_CONSTANT_NameAndType entry type, since there are two
+// data elements at the end of the recursions, we know that we have
+// between one and three unique entries. Any unique JVM_CONSTANT_Utf8
+// entries are appended to merge_cp before the current entry. For any
+// JVM_CONSTANT_Utf8 entries that are not unique, the current entry is
+// updated to refer to the duplicate entry in merge_cp before it is
+// appended to merge_cp. Again, any changes in index values are tracked
+// as needed.
+//
+// For the JVM_CONSTANT_{Fieldref,InterfaceMethodref,Methodref} entry
+// types, since there are two indirect CP entries and three data
+// elements at the end of the recursions, we know that we have between
+// one and six unique entries. See the JVM_CONSTANT_Fieldref diagram
+// above for an example of all six entries. The uniqueness algorithm
+// for the JVM_CONSTANT_Class and JVM_CONSTANT_NameAndType entries is
+// covered above. Any unique entries are appended to merge_cp before
+// the current entry. For any entries that are not unique, the current
+// entry is updated to refer to the duplicate entry in merge_cp before
+// it is appended to merge_cp. Again, any changes in index values are
+// tracked as needed.
+//
+//
+// Other Details:
+//
+// Details for other parts of RedefineClasses need to be written.
+// This is a placeholder section.
+//
+//
+// Open Issues (in no particular order):
+//
+// - How do we serialize the RedefineClasses() API without deadlocking?
+//
+// - SystemDictionary::parse_stream() was called with a NULL protection
+//   domain since the initial version. This has been changed to pass
+//   the_class->protection_domain(). This change has been tested with
+//   all NSK tests and nothing broke, but what will adding it now break
+//   in ways that we don't test?
+//
+// - GenerateOopMap::rewrite_load_or_store() has a comment in its
+//   (indirect) use of the Relocator class that the max instruction
+//   size is 4 bytes. goto_w and jsr_w are 5 bytes and wide/iinc is
+//   6 bytes. Perhaps Relocator only needs a 4 byte buffer to do
+//   what it does to the bytecodes. More investigation is needed.
+//
+// - java.lang.Object methods can be called on arrays. This is
+//   implemented via the arrayKlassOop vtable which we don't
+//   update. For example, if we redefine java.lang.Object.toString(),
+//   then the new version of the method will not be called for array
+//   objects.
+//
+// - How do we know if redefine_single_class() and the guts of
+//   instanceKlass are out of sync? I don't think this can be
+//   automated, but we should probably order the work in
+//   redefine_single_class() to match the order of field
+//   definitions in instanceKlass. We also need to add some
+//   comments about keeping things in sync.
+//
+// - set_new_constant_pool() is huge and we should consider refactoring
+//   it into smaller chunks of work.
+//
+// - The exception table update code in set_new_constant_pool() defines
+//   const values that are also defined in a local context elsewhere.
+//   The same literal values are also used in elsewhere. We need to
+//   coordinate a cleanup of these constants with Runtime.
+//
+
+class VM_RedefineClasses: public VM_Operation {
+ private:
+  // These static fields are needed by SystemDictionary::classes_do()
+  // facility and the adjust_cpool_cache_and_vtable() helper:
+  static objArrayOop     _old_methods;
+  static objArrayOop     _new_methods;
+  static methodOop*      _matching_old_methods;
+  static methodOop*      _matching_new_methods;
+  static methodOop*      _deleted_methods;
+  static methodOop*      _added_methods;
+  static int             _matching_methods_length;
+  static int             _deleted_methods_length;
+  static int             _added_methods_length;
+  static klassOop        _the_class_oop;
+
+  // The instance fields are used to pass information from
+  // doit_prologue() to doit() and doit_epilogue().
+  jint                        _class_count;
+  const jvmtiClassDefinition *_class_defs;  // ptr to _class_count defs
+
+  // This operation is used by both RedefineClasses and
+  // RetransformClasses.  Indicate which.
+  JvmtiClassLoadKind          _class_load_kind;
+
+  // _index_map_count is just an optimization for knowing if
+  // _index_map_p contains any entries.
+  int                         _index_map_count;
+  intArray *                  _index_map_p;
+  // ptr to _class_count scratch_classes
+  instanceKlassHandle *       _scratch_classes;
+  jvmtiError                  _res;
+
+  // Performance measurement support. These timers do not cover all
+  // the work done for JVM/TI RedefineClasses() but they do cover
+  // the heavy lifting.
+  elapsedTimer  _timer_rsc_phase1;
+  elapsedTimer  _timer_rsc_phase2;
+  elapsedTimer  _timer_vm_op_prologue;
+
+  // These routines are roughly in call order unless otherwise noted.
+
+  // Load the caller's new class definition(s) into _scratch_classes.
+  // Constant pool merging work is done here as needed. Also calls
+  // compare_and_normalize_class_versions() to verify the class
+  // definition(s).
+  jvmtiError load_new_class_versions(TRAPS);
+
+  // Verify that the caller provided class definition(s) that meet
+  // the restrictions of RedefineClasses. Normalize the order of
+  // overloaded methods as needed.
+  jvmtiError compare_and_normalize_class_versions(
+    instanceKlassHandle the_class, instanceKlassHandle scratch_class);
+
+  // Swap annotations[i] with annotations[j]
+  // Used by compare_and_normalize_class_versions() when normalizing
+  // overloaded methods or changing idnum as when adding or deleting methods.
+  void swap_all_method_annotations(int i, int j, instanceKlassHandle scratch_class);
+
+  // Figure out which new methods match old methods in name and signature,
+  // which methods have been added, and which are no longer present
+  void compute_added_deleted_matching_methods();
+
+  // Change jmethodIDs to point to the new methods
+  void update_jmethod_ids();
+
+  // In addition to marking methods as obsolete, this routine
+  // records which methods are EMCP (Equivalent Module Constant
+  // Pool) in the emcp_methods BitMap and returns the number of
+  // EMCP methods via emcp_method_count_p. This information is
+  // used when information about the previous version of the_class
+  // is squirreled away.
+  void check_methods_and_mark_as_obsolete(BitMap *emcp_methods,
+         int * emcp_method_count_p);
+  void transfer_old_native_function_registrations(instanceKlassHandle the_class);
+
+  // Unevolving classes may point to methods of the_class directly
+  // from their constant pool caches, itables, and/or vtables. We
+  // use the SystemDictionary::classes_do() facility and this helper
+  // to fix up these pointers.
+  static void adjust_cpool_cache_and_vtable(klassOop k_oop, oop loader, TRAPS);
+
+  // Install the redefinition of a class
+  void redefine_single_class(jclass the_jclass,
+    instanceKlassHandle scratch_class, TRAPS);
+
+  // Increment the classRedefinedCount field in the specific instanceKlass
+  // and in all direct and indirect subclasses.
+  void increment_class_counter(instanceKlass *ik, TRAPS);
+
+  // Support for constant pool merging (these routines are in alpha
+  // order):
+  void append_entry(constantPoolHandle scratch_cp, int scratch_i,
+    constantPoolHandle *merge_cp_p, int *merge_cp_length_p, TRAPS);
+  int find_new_index(int old_index);
+  bool is_unresolved_class_mismatch(constantPoolHandle cp1, int index1,
+    constantPoolHandle cp2, int index2);
+  bool is_unresolved_string_mismatch(constantPoolHandle cp1, int index1,
+    constantPoolHandle cp2, int index2);
+  void map_index(constantPoolHandle scratch_cp, int old_index, int new_index);
+  bool merge_constant_pools(constantPoolHandle old_cp,
+    constantPoolHandle scratch_cp, constantPoolHandle *merge_cp_p,
+    int *merge_cp_length_p, TRAPS);
+  jvmtiError merge_cp_and_rewrite(instanceKlassHandle the_class,
+    instanceKlassHandle scratch_class, TRAPS);
+  u2 rewrite_cp_ref_in_annotation_data(
+    typeArrayHandle annotations_typeArray, int &byte_i_ref,
+    const char * trace_mesg, TRAPS);
+  bool rewrite_cp_refs(instanceKlassHandle scratch_class, TRAPS);
+  bool rewrite_cp_refs_in_annotation_struct(
+    typeArrayHandle class_annotations, int &byte_i_ref, TRAPS);
+  bool rewrite_cp_refs_in_annotations_typeArray(
+    typeArrayHandle annotations_typeArray, int &byte_i_ref, TRAPS);
+  bool rewrite_cp_refs_in_class_annotations(
+    instanceKlassHandle scratch_class, TRAPS);
+  bool rewrite_cp_refs_in_element_value(
+    typeArrayHandle class_annotations, int &byte_i_ref, TRAPS);
+  bool rewrite_cp_refs_in_fields_annotations(
+    instanceKlassHandle scratch_class, TRAPS);
+  void rewrite_cp_refs_in_method(methodHandle method,
+    methodHandle * new_method_p, TRAPS);
+  bool rewrite_cp_refs_in_methods(instanceKlassHandle scratch_class, TRAPS);
+  bool rewrite_cp_refs_in_methods_annotations(
+    instanceKlassHandle scratch_class, TRAPS);
+  bool rewrite_cp_refs_in_methods_default_annotations(
+    instanceKlassHandle scratch_class, TRAPS);
+  bool rewrite_cp_refs_in_methods_parameter_annotations(
+    instanceKlassHandle scratch_class, TRAPS);
+  void rewrite_cp_refs_in_stack_map_table(methodHandle method, TRAPS);
+  void rewrite_cp_refs_in_verification_type_info(
+         address& stackmap_addr_ref, address stackmap_end, u2 frame_i,
+         u1 frame_size, TRAPS);
+  void set_new_constant_pool(instanceKlassHandle scratch_class,
+    constantPoolHandle scratch_cp, int scratch_cp_length, bool shrink, TRAPS);
+
+  void flush_dependent_code(instanceKlassHandle k_h, TRAPS);
+
+  static void check_class(klassOop k_oop, oop initiating_loader, TRAPS) PRODUCT_RETURN;
+
+  static void dump_methods()   PRODUCT_RETURN;
+
+ public:
+  VM_RedefineClasses(jint class_count,
+                     const jvmtiClassDefinition *class_defs,
+                     JvmtiClassLoadKind class_load_kind);
+  VMOp_Type type() const { return VMOp_RedefineClasses; }
+  bool doit_prologue();
+  void doit();
+  void doit_epilogue();
+
+  bool allow_nested_vm_operations() const        { return true; }
+  jvmtiError check_error()                       { return _res; }
+
+  // Modifiable test must be shared between IsModifiableClass query
+  // and redefine implementation
+  static bool is_modifiable_class(oop klass_mirror);
+};