1 /*
   2  * Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 #ifdef CHECK_UNHANDLED_OOPS
  25 
  26 // Detect unhanded oops in VM code
  27 
  28 // The design is that when an oop is declared on the stack as a local
  29 // variable, the oop is actually a C++ struct with constructor and
  30 // destructor.  The constructor adds the oop address on a list
  31 // off each thread and the destructor removes the oop.  At a potential
  32 // safepoint, the stack addresses of the local variable oops are trashed
  33 // with a recognizeable value.  If the local variable is used again, it
  34 // will segfault, indicating an unsafe use of that oop.
  35 // eg:
  36 //    oop o;    //register &o on list
  37 //    funct();  // if potential safepoint - causes clear_naked_oops()
  38 //              // which trashes o above.
  39 //    o->do_something();  // Crashes because o is unsafe.
  40 //
  41 // This code implements the details of the unhandled oop list on the thread.
  42 //
  43 
  44 class oop;
  45 class Thread;
  46 
  47 class UnhandledOopEntry {
  48  friend class UnhandledOops;
  49  private:
  50   oop* _oop_ptr;
  51   bool _ok_for_gc;
  52   address _pc;
  53  public:
  54   oop* oop_ptr() { return _oop_ptr; }
  55   UnhandledOopEntry() : _oop_ptr(NULL), _ok_for_gc(false), _pc(NULL) {}
  56   UnhandledOopEntry(oop* op, address pc) :
  57                         _oop_ptr(op),   _ok_for_gc(false), _pc(pc) {}
  58 };
  59 
  60 
  61 class UnhandledOops {
  62  friend class Thread;
  63  private:
  64   Thread* _thread;
  65   int _level;
  66   GrowableArray<UnhandledOopEntry> *_oop_list;
  67   void allow_unhandled_oop(oop* op);
  68   void clear_unhandled_oops();
  69   UnhandledOops(Thread* thread);
  70   ~UnhandledOops();
  71 
  72  public:
  73   static void dump_oops(UnhandledOops* list);
  74   void register_unhandled_oop(oop* op, address pc);
  75   void unregister_unhandled_oop(oop* op);
  76 };
  77 
  78 #ifdef _LP64
  79 const intptr_t BAD_OOP_ADDR =  0xfffffffffffffff1;
  80 #else
  81 const intptr_t BAD_OOP_ADDR =  0xfffffff1;
  82 #endif // _LP64
  83 #endif // CHECK_UNHANDLED_OOPS