8202035: Archive the set of ModuleDescriptor and ModuleReference objects for observable system modules with unnamed initial module

Support system module archiving with unnamed initial module at dump time.

Co-authored-by: Alan Bateman <alan.bateman@oracle.com>
Reviewed-by: erikj, coleenp, mchung, iklam, ccheung

src/hotspot/share/memory/heapShared.cpp

@@ -0,0 +1,506 @@
+/*
+ * Copyright (c) 2018, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "classfile/javaClasses.inline.hpp"
+#include "classfile/vmSymbols.hpp"
+#include "logging/log.hpp"
+#include "logging/logMessage.hpp"
+#include "logging/logStream.hpp"
+#include "memory/heapShared.hpp"
+#include "memory/iterator.inline.hpp"
+#include "memory/metadataFactory.hpp"
+#include "memory/metaspaceClosure.hpp"
+#include "memory/metaspaceShared.hpp"
+#include "memory/resourceArea.hpp"
+#include "oops/compressedOops.inline.hpp"
+#include "oops/oop.inline.hpp"
+
+#if INCLUDE_CDS_JAVA_HEAP
+KlassSubGraphInfo* HeapShared::_subgraph_info_list = NULL;
+int HeapShared::_num_archived_subgraph_info_records = 0;
+Array<ArchivedKlassSubGraphInfoRecord>* HeapShared::_archived_subgraph_info_records = NULL;
+
+// Currently there is only one class mirror (ArchivedModuleGraph) with archived
+// sub-graphs.
+KlassSubGraphInfo* HeapShared::find_subgraph_info(Klass* k) {
+  KlassSubGraphInfo* info = _subgraph_info_list;
+  while (info != NULL) {
+    if (info->klass() == k) {
+      return info;
+    }
+    info = info->next();
+  }
+  return NULL;
+}
+
+// Get the subgraph_info for Klass k. A new subgraph_info is created if
+// there is no existing one for k. The subgraph_info records the relocated
+// Klass* of the original k.
+KlassSubGraphInfo* HeapShared::get_subgraph_info(Klass* k) {
+  Klass* relocated_k = MetaspaceShared::get_relocated_klass(k);
+  KlassSubGraphInfo* info = find_subgraph_info(relocated_k);
+  if (info != NULL) {
+    return info;
+  }
+
+  info = new KlassSubGraphInfo(relocated_k, _subgraph_info_list);
+  _subgraph_info_list = info;
+  return info;
+}
+
+int HeapShared::num_of_subgraph_infos() {
+  int num = 0;
+  KlassSubGraphInfo* info = _subgraph_info_list;
+  while (info != NULL) {
+    num ++;
+    info = info->next();
+  }
+  return num;
+}
+
+// Add an entry field to the current KlassSubGraphInfo.
+void KlassSubGraphInfo::add_subgraph_entry_field(int static_field_offset, oop v) {
+  assert(DumpSharedSpaces, "dump time only");
+  if (_subgraph_entry_fields == NULL) {
+    _subgraph_entry_fields =
+      new(ResourceObj::C_HEAP, mtClass) GrowableArray<juint>(10, true);
+  }
+  _subgraph_entry_fields->append((juint)static_field_offset);
+  _subgraph_entry_fields->append(CompressedOops::encode(v));
+}
+
+// Add the Klass* for an object in the current KlassSubGraphInfo's subgraphs.
+// Only objects of boot classes can be included in sub-graph.
+void KlassSubGraphInfo::add_subgraph_object_klass(Klass* orig_k, Klass *relocated_k) {
+  assert(DumpSharedSpaces, "dump time only");
+  assert(relocated_k == MetaspaceShared::get_relocated_klass(orig_k),
+         "must be the relocated Klass in the shared space");
+
+  if (_subgraph_object_klasses == NULL) {
+    _subgraph_object_klasses =
+      new(ResourceObj::C_HEAP, mtClass) GrowableArray<Klass*>(50, true);
+  }
+
+  assert(relocated_k->is_shared(), "must be a shared class");
+  if (relocated_k->is_instance_klass()) {
+    assert(InstanceKlass::cast(relocated_k)->is_shared_boot_class(),
+          "must be boot class");
+    // SystemDictionary::xxx_klass() are not updated, need to check
+    // the original Klass*
+    if (orig_k == SystemDictionary::String_klass() ||
+        orig_k == SystemDictionary::Object_klass()) {
+      // Initialized early during VM initialization. No need to be added
+      // to the sub-graph object class list.
+      return;
+    }
+  } else if (relocated_k->is_objArray_klass()) {
+    Klass* abk = ObjArrayKlass::cast(relocated_k)->bottom_klass();
+    if (abk->is_instance_klass()) {
+      assert(InstanceKlass::cast(abk)->is_shared_boot_class(),
+            "must be boot class");
+    }
+    if (relocated_k == Universe::objectArrayKlassObj()) {
+      // Initialized early during Universe::genesis. No need to be added
+      // to the list.
+      return;
+    }
+  } else {
+    assert(relocated_k->is_typeArray_klass(), "must be");
+    // Primitive type arrays are created early during Universe::genesis.
+    return;
+  }
+
+  _subgraph_object_klasses->append_if_missing(relocated_k);
+}
+
+// Initialize an archived subgraph_info_record from the given KlassSubGraphInfo.
+void ArchivedKlassSubGraphInfoRecord::init(KlassSubGraphInfo* info) {
+  _k = info->klass();
+  _next = NULL;
+  _entry_field_records = NULL;
+  _subgraph_klasses = NULL;
+
+  // populate the entry fields
+  GrowableArray<juint>* entry_fields = info->subgraph_entry_fields();
+  if (entry_fields != NULL) {
+    int num_entry_fields = entry_fields->length();
+    assert(num_entry_fields % 2 == 0, "sanity");
+    _entry_field_records =
+      MetaspaceShared::new_ro_array<juint>(num_entry_fields);
+    for (int i = 0 ; i < num_entry_fields; i++) {
+      _entry_field_records->at_put(i, entry_fields->at(i));
+    }
+  }
+
+  // the Klasses of the objects in the sub-graphs
+  GrowableArray<Klass*>* subgraph_klasses = info->subgraph_object_klasses();
+  if (subgraph_klasses != NULL) {
+    int num_subgraphs_klasses = subgraph_klasses->length();
+    _subgraph_klasses =
+      MetaspaceShared::new_ro_array<Klass*>(num_subgraphs_klasses);
+    for (int i = 0; i < num_subgraphs_klasses; i++) {
+      Klass* subgraph_k = subgraph_klasses->at(i);
+      if (log_is_enabled(Info, cds, heap)) {
+        ResourceMark rm;
+        log_info(cds, heap)(
+          "Archived object klass (%d): %s in %s sub-graphs",
+          i, subgraph_k->external_name(), _k->external_name());
+      }
+      _subgraph_klasses->at_put(i, subgraph_k);
+    }
+  }
+}
+
+// Build the records of archived subgraph infos, which include:
+// - Entry points to all subgraphs from the containing class mirror. The entry
+//   points are static fields in the mirror. For each entry point, the field
+//   offset and value are recorded in the sub-graph info. The value are stored
+//   back to the corresponding field at runtime.
+// - A list of klasses that need to be loaded/initialized before archived
+//   java object sub-graph can be accessed at runtime.
+//
+// The records are saved in the archive file and reloaded at runtime. Currently
+// there is only one class mirror (ArchivedModuleGraph) with archived sub-graphs.
+//
+// Layout of the archived subgraph info records:
+//
+// records_size | num_records | records*
+// ArchivedKlassSubGraphInfoRecord | entry_fields | subgraph_object_klasses
+size_t HeapShared::build_archived_subgraph_info_records(int num_records) {
+  // remember the start address
+  char* start_p = MetaspaceShared::read_only_space_top();
+
+  // now populate the archived subgraph infos, which will be saved in the
+  // archive file
+  _archived_subgraph_info_records =
+    MetaspaceShared::new_ro_array<ArchivedKlassSubGraphInfoRecord>(num_records);
+  KlassSubGraphInfo* info = _subgraph_info_list;
+  int i = 0;
+  while (info != NULL) {
+    assert(i < _archived_subgraph_info_records->length(), "sanity");
+    ArchivedKlassSubGraphInfoRecord* record =
+      _archived_subgraph_info_records->adr_at(i);
+    record->init(info);
+    info = info->next();
+    i ++;
+  }
+
+  // _subgraph_info_list is no longer needed
+  delete _subgraph_info_list;
+  _subgraph_info_list = NULL;
+
+  char* end_p = MetaspaceShared::read_only_space_top();
+  size_t records_size = end_p - start_p;
+  return records_size;
+}
+
+// Write the subgraph info records in the shared _ro region
+void HeapShared::write_archived_subgraph_infos() {
+  assert(DumpSharedSpaces, "dump time only");
+
+  Array<intptr_t>* records_header = MetaspaceShared::new_ro_array<intptr_t>(3);
+
+  _num_archived_subgraph_info_records = num_of_subgraph_infos();
+  size_t records_size = build_archived_subgraph_info_records(
+                             _num_archived_subgraph_info_records);
+
+  // Now write the header information:
+  // records_size, num_records, _archived_subgraph_info_records
+  assert(records_header != NULL, "sanity");
+  intptr_t* p = (intptr_t*)(records_header->data());
+  *p = (intptr_t)records_size;
+  p ++;
+  *p = (intptr_t)_num_archived_subgraph_info_records;
+  p ++;
+  *p = (intptr_t)_archived_subgraph_info_records;
+}
+
+char* HeapShared::read_archived_subgraph_infos(char* buffer) {
+  Array<intptr_t>* records_header = (Array<intptr_t>*)buffer;
+  intptr_t* p = (intptr_t*)(records_header->data());
+  size_t records_size = (size_t)(*p);
+  p ++;
+  _num_archived_subgraph_info_records = *p;
+  p ++;
+  _archived_subgraph_info_records =
+    (Array<ArchivedKlassSubGraphInfoRecord>*)(*p);
+
+  buffer = (char*)_archived_subgraph_info_records + records_size;
+  return buffer;
+}
+
+void HeapShared::initialize_from_archived_subgraph(Klass* k) {
+  if (!MetaspaceShared::open_archive_heap_region_mapped()) {
+    return; // nothing to do
+  }
+
+  if (_num_archived_subgraph_info_records == 0) {
+    return; // no subgraph info records
+  }
+
+  // Initialize from archived data. Currently only ArchivedModuleGraph
+  // has archived object subgraphs, which is used during VM initialization
+  // time when bootstraping the system modules. No lock is needed.
+  Thread* THREAD = Thread::current();
+  for (int i = 0; i < _archived_subgraph_info_records->length(); i++) {
+    ArchivedKlassSubGraphInfoRecord* record = _archived_subgraph_info_records->adr_at(i);
+    if (record->klass() == k) {
+      int i;
+      // Found the archived subgraph info record for the requesting klass.
+      // Load/link/initialize the klasses of the objects in the subgraph.
+      // NULL class loader is used.
+      Array<Klass*>* klasses = record->subgraph_klasses();
+      if (klasses != NULL) {
+        for (i = 0; i < klasses->length(); i++) {
+          Klass* obj_k = klasses->at(i);
+          Klass* resolved_k = SystemDictionary::resolve_or_null(
+                                                (obj_k)->name(), THREAD);
+          if (resolved_k != obj_k) {
+            return;
+          }
+          if ((obj_k)->is_instance_klass()) {
+            InstanceKlass* ik = InstanceKlass::cast(obj_k);
+            ik->initialize(THREAD);
+          } else if ((obj_k)->is_objArray_klass()) {
+            ObjArrayKlass* oak = ObjArrayKlass::cast(obj_k);
+            oak->initialize(THREAD);
+          }
+        }
+      }
+
+      if (HAS_PENDING_EXCEPTION) {
+        CLEAR_PENDING_EXCEPTION;
+        // None of the field value will be set if there was an exception.
+        // The java code will not see any of the archived objects in the
+        // subgraphs referenced from k in this case.
+        return;
+      }
+
+      // Load the subgraph entry fields from the record and store them back to
+      // the corresponding fields within the mirror.
+      oop m = k->java_mirror();
+      Array<juint>* entry_field_records = record->entry_field_records();
+      if (entry_field_records != NULL) {
+        int efr_len = entry_field_records->length();
+        assert(efr_len % 2 == 0, "sanity");
+        for (i = 0; i < efr_len;) {
+          int field_offset = entry_field_records->at(i);
+          // The object refereced by the field becomes 'known' by GC from this
+          // point. All objects in the subgraph reachable from the object are
+          // also 'known' by GC.
+          oop v = MetaspaceShared::materialize_archived_object(
+            CompressedOops::decode(entry_field_records->at(i+1)));
+          m->obj_field_put(field_offset, v);
+          i += 2;
+        }
+      }
+
+      // Done. Java code can see the archived sub-graphs referenced from k's
+      // mirror after this point.
+      return;
+    }
+  }
+}
+
+class WalkOopAndArchiveClosure: public BasicOopIterateClosure {
+  int _level;
+  KlassSubGraphInfo* _subgraph_info;
+  oop _orig_referencing_obj;
+  oop _archived_referencing_obj;
+ public:
+  WalkOopAndArchiveClosure(int level, KlassSubGraphInfo* subgraph_info,
+           oop orig, oop archived) : _level(level),
+                                     _subgraph_info(subgraph_info),
+                                     _orig_referencing_obj(orig),
+                                     _archived_referencing_obj(archived) {}
+  void do_oop(narrowOop *p) { WalkOopAndArchiveClosure::do_oop_work(p); }
+  void do_oop(      oop *p) { WalkOopAndArchiveClosure::do_oop_work(p); }
+
+ protected:
+  template <class T> void do_oop_work(T *p) {
+    oop obj = RawAccess<>::oop_load(p);
+    if (!CompressedOops::is_null(obj)) {
+      // A java.lang.Class instance can not be included in an archived
+      // object sub-graph.
+      if (java_lang_Class::is_instance(obj)) {
+        tty->print("Unknown java.lang.Class object is in the archived sub-graph\n");
+        vm_exit(1);
+      }
+
+      LogTarget(Debug, cds, heap) log;
+      LogStream ls(log);
+      outputStream* out = &ls;
+      {
+        ResourceMark rm;
+        log.print("(%d) %s <--- referenced from:  %s",
+                  _level, obj->klass()->external_name(),
+                  CompressedOops::is_null(_orig_referencing_obj) ?
+                         "" : _orig_referencing_obj->klass()->external_name());
+        obj->print_on(out);
+      }
+
+      if (MetaspaceShared::is_archive_object(obj)) {
+        // The current oop is an archived oop, nothing needs to be done
+        log.print("--- object is already archived ---");
+        return;
+      }
+
+      size_t field_delta = pointer_delta(
+        p, _orig_referencing_obj, sizeof(char));
+      T* new_p = (T*)(address(_archived_referencing_obj) + field_delta);
+      oop archived = MetaspaceShared::find_archived_heap_object(obj);
+      if (archived != NULL) {
+        // There is an archived copy existing, update reference to point
+        // to the archived copy
+        RawAccess<IS_NOT_NULL>::oop_store(new_p, archived);
+        log.print(
+          "--- found existing archived copy, store archived " PTR_FORMAT " in " PTR_FORMAT,
+          p2i(archived), p2i(new_p));
+        return;
+      }
+
+      int l = _level + 1;
+      Thread* THREAD = Thread::current();
+      // Archive the current oop before iterating through its references
+      archived = MetaspaceShared::archive_heap_object(obj, THREAD);
+      assert(MetaspaceShared::is_archive_object(archived), "must be archived");
+      log.print("=== archiving oop " PTR_FORMAT " ==> " PTR_FORMAT,
+                 p2i(obj), p2i(archived));
+
+      // Following the references in the current oop and archive any
+      // encountered objects during the process
+      WalkOopAndArchiveClosure walker(l, _subgraph_info, obj, archived);
+      obj->oop_iterate(&walker);
+
+      // Update the reference in the archived copy of the referencing object
+      RawAccess<IS_NOT_NULL>::oop_store(new_p, archived);
+      log.print("=== store archived " PTR_FORMAT " in " PTR_FORMAT,
+                p2i(archived), p2i(new_p));
+
+      // Add the klass to the list of classes that need to be loaded before
+      // module system initialization
+      Klass *orig_k = obj->klass();
+      Klass *relocated_k = archived->klass();
+      _subgraph_info->add_subgraph_object_klass(orig_k, relocated_k);
+    }
+  }
+};
+
+//
+// Start from the given static field in a java mirror and archive the
+// complete sub-graph of java heap objects that are reached directly
+// or indirectly from the starting object by following references.
+// Currently, only ArchivedModuleGraph class instance (mirror) has archived
+// object subgraphs. Sub-graph archiving restrictions (current):
+//
+// - All classes of objects in the archived sub-graph (including the
+//   entry class) must be boot class only.
+// - No java.lang.Class instance (java mirror) can be included inside
+//   an archived sub-graph. Mirror can only be the sub-graph entry object.
+//
+// The Java heap object sub-graph archiving process (see
+// WalkOopAndArchiveClosure):
+//
+// 1) Java object sub-graph archiving starts from a given static field
+// within a Class instance (java mirror). If the static field is a
+// refererence field and points to a non-null java object, proceed to
+// the next step.
+//
+// 2) Archives the referenced java object. If an archived copy of the
+// current object already exists, updates the pointer in the archived
+// copy of the referencing object to point to the current archived object.
+// Otherwise, proceed to the next step.
+//
+// 3) Follows all references within the current java object and recursively
+// archive the sub-graph of objects starting from each reference.
+//
+// 4) Updates the pointer in the archived copy of referencing object to
+//    point to the current archived object.
+//
+// 5) The Klass of the current java object is added to the list of Klasses
+// for loading and initialzing before any object in the archived graph can
+// be accessed at runtime.
+//
+void HeapShared::archive_reachable_objects_from_static_field(Klass *k,
+                                                             int field_offset,
+                                                             BasicType field_type,
+                                                             TRAPS) {
+  assert(DumpSharedSpaces, "dump time only");
+  assert(k->is_instance_klass(), "sanity");
+  assert(InstanceKlass::cast(k)->is_shared_boot_class(),
+         "must be boot class");
+
+  oop m = k->java_mirror();
+  oop archived_m = MetaspaceShared::find_archived_heap_object(m);
+  if (CompressedOops::is_null(archived_m)) {
+    return;
+  }
+
+  if (field_type == T_OBJECT) {
+    // obtain k's subGraph Info
+    KlassSubGraphInfo* subgraph_info = get_subgraph_info(k);
+
+    // get the object referenced by the field
+    oop f = m->obj_field(field_offset);
+    if (!CompressedOops::is_null(f)) {
+      LogTarget(Debug, cds, heap) log;
+      LogStream ls(log);
+      outputStream* out = &ls;
+      log.print("Start from: ");
+      f->print_on(out);
+
+      // get the archived copy of the field referenced object
+      oop af = MetaspaceShared::archive_heap_object(f, THREAD);
+      if (!MetaspaceShared::is_archive_object(f)) {
+        WalkOopAndArchiveClosure walker(1, subgraph_info, f, af);
+        f->oop_iterate(&walker);
+      }
+
+      // The field value is not preserved in the archived mirror.
+      // Record the field as a new subGraph entry point. The recorded
+      // information is restored from the archive at runtime.
+      subgraph_info->add_subgraph_entry_field(field_offset, af);
+      Klass *relocated_k = af->klass();
+      Klass *orig_k = f->klass();
+      subgraph_info->add_subgraph_object_klass(orig_k, relocated_k);
+    } else {
+      // The field contains null, we still need to record the entry point,
+      // so it can be restored at runtime.
+      subgraph_info->add_subgraph_entry_field(field_offset, NULL);
+    }
+  } else {
+    ShouldNotReachHere();
+  }
+}
+
+#define do_module_object_graph(archive_object_graph_do) \
+  archive_object_graph_do(SystemDictionary::ArchivedModuleGraph_klass(), jdk_internal_module_ArchivedModuleGraph::archivedSystemModules_offset(), T_OBJECT, CHECK); \
+  archive_object_graph_do(SystemDictionary::ArchivedModuleGraph_klass(), jdk_internal_module_ArchivedModuleGraph::archivedModuleFinder_offset(), T_OBJECT, CHECK); \
+  archive_object_graph_do(SystemDictionary::ArchivedModuleGraph_klass(), jdk_internal_module_ArchivedModuleGraph::archivedMainModule_offset(), T_OBJECT, CHECK)
+
+void HeapShared::archive_module_graph_objects(Thread* THREAD) {
+  do_module_object_graph(archive_reachable_objects_from_static_field);
+}
+#endif // INCLUDE_CDS_JAVA_HEAP