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 /*

  * Copyright (c) 2014, 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.hpp"

 #include "jfr/leakprofiler/chains/edge.hpp"

 #include "jfr/leakprofiler/chains/edgeStore.hpp"

 #include "jfr/leakprofiler/chains/edgeUtils.hpp"

 #include "jfr/leakprofiler/utilities/unifiedOop.hpp"

 #include "oops/fieldStreams.hpp"

 #include "oops/instanceKlass.hpp"

 #include "oops/objArrayOop.hpp"

 #include "oops/oopsHierarchy.hpp"

 #include "runtime/handles.inline.hpp"

 bool EdgeUtils::is_leak_edge(const Edge& edge) {

   return (const Edge*)edge.pointee()->mark() == &edge;

 }

 bool EdgeUtils::is_root(const Edge& edge) {

   return edge.is_root();

 }

 static int field_offset(const Edge& edge) {

   assert(!edge.is_root(), "invariant");

   const oop ref_owner = edge.reference_owner();

   assert(ref_owner != NULL, "invariant");

   const oop* reference = UnifiedOop::decode(edge.reference());

   assert(reference != NULL, "invariant");

   assert(!UnifiedOop::is_narrow(reference), "invariant");

   assert(!ref_owner->is_array(), "invariant");

   assert(ref_owner->is_instance(), "invariant");

   const int offset = (int)pointer_delta(reference, ref_owner, sizeof(char));

   assert(offset < (ref_owner->size() * HeapWordSize), "invariant");

   return offset;

 }

 static const InstanceKlass* field_type(const Edge& edge) {

   assert(!edge.is_root() || !EdgeUtils::is_array_element(edge), "invariant");

   return (const InstanceKlass*)edge.reference_owner_klass();

 }

 const Symbol* EdgeUtils::field_name_symbol(const Edge& edge) {

   assert(!edge.is_root(), "invariant");

   assert(!is_array_element(edge), "invariant");

   const int offset = field_offset(edge);

   const InstanceKlass* ik = field_type(edge);

   while (ik != NULL) {

     JavaFieldStream jfs(ik);

     while (!jfs.done()) {

       if (offset == jfs.offset()) {

         return jfs.name();

       }

       jfs.next();

     }

     ik = (InstanceKlass*)ik->super();

   }

   return NULL;

 }

 jshort EdgeUtils::field_modifiers(const Edge& edge) {

   const int offset = field_offset(edge);

   const InstanceKlass* ik = field_type(edge);

   while (ik != NULL) {

     JavaFieldStream jfs(ik);

     while (!jfs.done()) {

       if (offset == jfs.offset()) {

         return jfs.access_flags().as_short();

       }

       jfs.next();

     }

     ik = (InstanceKlass*)ik->super();

   }

   return 0;

 }

 bool EdgeUtils::is_array_element(const Edge& edge) {

   assert(!edge.is_root(), "invariant");

   const oop ref_owner = edge.reference_owner();

   assert(ref_owner != NULL, "invariant");

   return ref_owner->is_objArray();

 }

 static int array_offset(const Edge& edge) {

   assert(!edge.is_root(), "invariant");

   const oop ref_owner = edge.reference_owner();

   assert(ref_owner != NULL, "invariant");

   const oop* reference = UnifiedOop::decode(edge.reference());

   assert(reference != NULL, "invariant");

   assert(!UnifiedOop::is_narrow(reference), "invariant");

   assert(ref_owner->is_array(), "invariant");

   const objArrayOop ref_owner_array = static_cast<const objArrayOop>(ref_owner);

   const int offset = (int)pointer_delta(reference, ref_owner_array->base(), heapOopSize);

   assert(offset >= 0 && offset < ref_owner_array->length(), "invariant");

   return offset;

 }

 int EdgeUtils::array_index(const Edge& edge) {

   return is_array_element(edge) ? array_offset(edge) : 0;

 }

 int EdgeUtils::array_size(const Edge& edge) {

   if (is_array_element(edge)) {

     const oop ref_owner = edge.reference_owner();

     assert(ref_owner != NULL, "invariant");

     assert(ref_owner->is_objArray(), "invariant");

     return ((objArrayOop)(ref_owner))->length();

   }

   return 0;

 }

 const Edge* EdgeUtils::root(const Edge& edge) {

   const Edge* current = &edge;

   const Edge* parent = current->parent();

   while (parent != NULL) {

     current = parent;

     parent = current->parent();

   }

   return current;

 }

 // The number of references associated with the leak node;

 // can be viewed as the leak node "context".

 // Used to provide leak context for a "capped/skipped" reference chain.

 static const size_t leak_context = 100;

 // The number of references associated with the root node;

 // can be viewed as the root node "context".

 // Used to provide root context for a "capped/skipped" reference chain.

 static const size_t root_context = 100;

 // A limit on the reference chain depth to be serialized,

 static const size_t max_ref_chain_depth = leak_context + root_context;

 const RoutableEdge* skip_to(const RoutableEdge& edge, size_t skip_length) {

   const RoutableEdge* current = &edge;

   const RoutableEdge* parent = current->physical_parent();

   size_t seek = 0;

   while (parent != NULL && seek != skip_length) {

     seek++;

     current = parent;

     parent = parent->physical_parent();

   }

   return current;

 }

 #ifdef ASSERT

 static void validate_skip_target(const RoutableEdge* skip_target) {

   assert(skip_target != NULL, "invariant");

   assert(skip_target->distance_to_root() + 1 == root_context, "invariant");

   assert(skip_target->is_sentinel(), "invariant");

 }

 static void validate_new_skip_edge(const RoutableEdge* new_skip_edge, const RoutableEdge* last_skip_edge, size_t adjustment) {

   assert(new_skip_edge != NULL, "invariant");

   assert(new_skip_edge->is_skip_edge(), "invariant");

   if (last_skip_edge != NULL) {

     const RoutableEdge* const target = skip_to(*new_skip_edge->logical_parent(), adjustment);

     validate_skip_target(target->logical_parent());

     return;

   }

   assert(last_skip_edge == NULL, "invariant");

   // only one level of logical indirection

   validate_skip_target(new_skip_edge->logical_parent());

 }

 #endif // ASSERT

 static void install_logical_route(const RoutableEdge* new_skip_edge, size_t skip_target_distance) {

   assert(new_skip_edge != NULL, "invariant");

   assert(!new_skip_edge->is_skip_edge(), "invariant");

   assert(!new_skip_edge->processed(), "invariant");

   const RoutableEdge* const skip_target = skip_to(*new_skip_edge, skip_target_distance);

   assert(skip_target != NULL, "invariant");

   new_skip_edge->set_skip_edge(skip_target);

   new_skip_edge->set_skip_length(skip_target_distance);

   assert(new_skip_edge->is_skip_edge(), "invariant");

   assert(new_skip_edge->logical_parent() == skip_target, "invariant");

 }

 static const RoutableEdge* find_last_skip_edge(const RoutableEdge& edge, size_t& distance) {

   assert(distance == 0, "invariant");

   const RoutableEdge* current = &edge;

   while (current != NULL) {

     if (current->is_skip_edge() && current->skip_edge()->is_sentinel()) {

       return current;

     }

     current = current->physical_parent();

     ++distance;

   }

   return current;

 }

 static void collapse_overlapping_chain(const RoutableEdge& edge,

                                        const RoutableEdge* first_processed_edge,

                                        size_t first_processed_distance) {

   assert(first_processed_edge != NULL, "invariant");

   // first_processed_edge is already processed / written

   assert(first_processed_edge->processed(), "invariant");

   assert(first_processed_distance + 1 <= leak_context, "invariant");

   // from this first processed edge, attempt to fetch the last skip edge

   size_t last_skip_edge_distance = 0;

   const RoutableEdge* const last_skip_edge = find_last_skip_edge(*first_processed_edge, last_skip_edge_distance);

   const size_t distance_discovered = first_processed_distance + last_skip_edge_distance + 1;

   if (distance_discovered <= leak_context || (last_skip_edge == NULL && distance_discovered <= max_ref_chain_depth)) {

     // complete chain can be accommodated without modification

     return;

   }

   // backtrack one edge from existing processed edge

   const RoutableEdge* const new_skip_edge = skip_to(edge, first_processed_distance - 1);

   assert(new_skip_edge != NULL, "invariant");

   assert(!new_skip_edge->processed(), "invariant");

   assert(new_skip_edge->parent() == first_processed_edge, "invariant");

   size_t adjustment = 0;

   if (last_skip_edge != NULL) {

     assert(leak_context - 1 > first_processed_distance - 1, "invariant");

     adjustment = leak_context - first_processed_distance - 1;

     assert(last_skip_edge_distance + 1 > adjustment, "invariant");

     install_logical_route(new_skip_edge, last_skip_edge_distance + 1 - adjustment);

   } else {

     install_logical_route(new_skip_edge, last_skip_edge_distance + 1 - root_context);

     new_skip_edge->logical_parent()->set_skip_length(1); // sentinel

   }

   DEBUG_ONLY(validate_new_skip_edge(new_skip_edge, last_skip_edge, adjustment);)

 }

 static void collapse_non_overlapping_chain(const RoutableEdge& edge,

                                            const RoutableEdge* first_processed_edge,

                                            size_t first_processed_distance) {

   assert(first_processed_edge != NULL, "invariant");

   assert(!first_processed_edge->processed(), "invariant");

   // this implies that the first "processed" edge is the leak context relative "leaf"

   assert(first_processed_distance + 1 == leak_context, "invariant");

   const size_t distance_to_root = edge.distance_to_root();

   if (distance_to_root + 1 <= max_ref_chain_depth) {

     // complete chain can be accommodated without constructing a skip edge

     return;

   }

   install_logical_route(first_processed_edge, distance_to_root + 1 - first_processed_distance - root_context);

   first_processed_edge->logical_parent()->set_skip_length(1); // sentinel

   DEBUG_ONLY(validate_new_skip_edge(first_processed_edge, NULL, 0);)

 }

 static const RoutableEdge* processed_edge(const RoutableEdge& edge, size_t& distance) {

   assert(distance == 0, "invariant");

   const RoutableEdge* current = &edge;

   while (current != NULL && distance < leak_context - 1) {

     if (current->processed()) {

       return current;

     }

     current = current->physical_parent();

     ++distance;

   }

   assert(distance <= leak_context - 1, "invariant");

   return current;

 }

 /*

  * Some vocabulary:

  * -----------

  * "Context" is an interval in the chain, it is associcated with an edge and it signifies a number of connected edges.

  * "Processed / written" means an edge that has already been serialized.

  * "Skip edge" is an edge that contains additional information for logical routing purposes.

  * "Skip target" is an edge used as a destination for a skip edge

  */

 void EdgeUtils::collapse_chain(const RoutableEdge& edge) {

   assert(is_leak_edge(edge), "invariant");

   // attempt to locate an already processed edge inside current leak context (if any)

   size_t first_processed_distance = 0;

   const RoutableEdge* const first_processed_edge = processed_edge(edge, first_processed_distance);

   if (first_processed_edge == NULL) {

     return;

   }

   if (first_processed_edge->processed()) {

     collapse_overlapping_chain(edge, first_processed_edge, first_processed_distance);

   } else {

     collapse_non_overlapping_chain(edge, first_processed_edge, first_processed_distance);

   }

   assert(edge.logical_distance_to_root() + 1 <= max_ref_chain_depth, "invariant");

 }