src/hotspot/share/runtime/unhandledOops.cpp

/*
 * Copyright (c) 2005, 2025, 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 "gc/shared/collectedHeap.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/javaThread.hpp"
#include "runtime/unhandledOops.hpp"
#include "utilities/globalDefinitions.hpp"

#ifdef CHECK_UNHANDLED_OOPS
const int free_list_size = 256;


UnhandledOops::UnhandledOops(Thread* thread) {
  _thread = thread;
  _oop_list = new (mtThread)
                    GrowableArray<UnhandledOopEntry>(free_list_size, mtThread);
  _level = 0;
}

UnhandledOops::~UnhandledOops() {
  delete _oop_list;
}


void UnhandledOops::dump_oops(UnhandledOops *list) {
  for (int k = 0; k < list->_oop_list->length(); k++) {
    UnhandledOopEntry entry = list->_oop_list->at(k);
    tty->print(" " INTPTR_FORMAT, p2i(entry._oop_ptr));
  }
  tty->cr();
}

// For debugging unhandled oop detector _in the debugger_
// You don't want to turn it on in compiled code here.
static Thread* unhandled_oop_print = nullptr;

void UnhandledOops::register_unhandled_oop(oop* op) {
  if (!_thread->is_in_live_stack((address)op)) {
    return;
  }

  _level++;
  if (unhandled_oop_print == _thread) {
    for (int i=0; i < _level; i++) tty->print(" ");
    tty->print_cr("r " INTPTR_FORMAT, p2i(op));
  }
  UnhandledOopEntry entry(op);
  _oop_list->push(entry);
}

// Mark unhandled oop as okay for GC - the containing struct has an oops_do and
// for some reason the oop has to be on the stack.
// May not be called for the current thread, as in the case of
// VM_GetOrSetLocal in jvmti.
void UnhandledOops::allow_unhandled_oop(oop* op) {
  assert (CheckUnhandledOops, "should only be called with checking option");

  int i = _oop_list->find_from_end_if([&](const UnhandledOopEntry& e) {
    return e.match_oop_entry(op);
  });
  assert(i!=-1, "safe for gc oop not in unhandled_oop_list");

  UnhandledOopEntry entry = _oop_list->at(i);
  assert(!entry._ok_for_gc, "duplicate entry");
  entry._ok_for_gc = true;
  _oop_list->at_put(i, entry);
}


// Called by the oop destructor to remove unhandled oop from the thread's
// oop list.  All oops given are assumed to be on the list.  If not,
// there's a bug in the unhandled oop detector.
void UnhandledOops::unregister_unhandled_oop(oop* op) {
  if (!_thread->is_in_live_stack((address)op)) return;

  if (unhandled_oop_print == _thread) {
    for (int i=0; i < _level; i++) tty->print(" ");
    tty->print_cr("u " INTPTR_FORMAT, p2i(op));
  }
  _level--;

  int i = _oop_list->find_from_end_if([&](const UnhandledOopEntry& e) {
    return e.match_oop_entry(op);
  });
  assert(i!=-1, "oop not in unhandled_oop_list");
  _oop_list->remove_at(i);
}

void UnhandledOops::clear_unhandled_oops() {
  assert (CheckUnhandledOops, "should only be called with checking option");

  for (int k = 0; k < _oop_list->length(); k++) {
    UnhandledOopEntry entry = _oop_list->at(k);
    // If an entry is on the unhandled oop list but isn't on the stack
    // anymore, it must not have gotten unregistered properly and it's a bug
    // in the unhandled oop generator.
    if (!_thread->is_in_live_stack((address)entry._oop_ptr)) {
      tty->print_cr("oop_ptr is " INTPTR_FORMAT, p2i(entry._oop_ptr));
      tty->print_cr("thread is " INTPTR_FORMAT, p2i(_thread));
      assert(false, "heap is corrupted by the unhandled oop detector");
    }
    // Set unhandled oops to a pattern that will crash distinctively
    if (!entry._ok_for_gc) *(intptr_t*)(entry._oop_ptr) = BAD_OOP_ADDR;
  }
}
#endif // CHECK_UNHANDLED_OOPS