1 /*
   2  * Copyright (c) 2005, 2010, 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 
  25 #ifndef SHARE_VM_RUNTIME_UNHANDLEDOOPS_HPP
  26 #define SHARE_VM_RUNTIME_UNHANDLEDOOPS_HPP
  27 
  28 #ifdef CHECK_UNHANDLED_OOPS
  29 
  30 // Detect unhanded oops in VM code
  31 
  32 // The design is that when an oop is declared on the stack as a local
  33 // variable, the oop is actually a C++ struct with constructor and
  34 // destructor.  The constructor adds the oop address on a list
  35 // off each thread and the destructor removes the oop.  At a potential
  36 // safepoint, the stack addresses of the local variable oops are trashed
  37 // with a recognizable value.  If the local variable is used again, it
  38 // will segfault, indicating an unsafe use of that oop.
  39 // eg:
  40 //    oop o;    //register &o on list
  41 //    funct();  // if potential safepoint - causes clear_naked_oops()
  42 //              // which trashes o above.
  43 //    o->do_something();  // Crashes because o is unsafe.
  44 //
  45 // This code implements the details of the unhandled oop list on the thread.
  46 //
  47 
  48 class oop;
  49 class Thread;
  50 
  51 class UnhandledOopEntry : public CHeapObj<mtThread> {
  52  friend class UnhandledOops;
  53  private:
  54   oop* _oop_ptr;
  55   bool _ok_for_gc;
  56   address _pc;
  57  public:
  58   oop* oop_ptr() { return _oop_ptr; }
  59   UnhandledOopEntry() : _oop_ptr(NULL), _ok_for_gc(false), _pc(NULL) {}
  60   UnhandledOopEntry(oop* op, address pc) :
  61                         _oop_ptr(op),   _ok_for_gc(false), _pc(pc) {}
  62 };
  63 
  64 
  65 class UnhandledOops : public CHeapObj<mtThread> {
  66  friend class Thread;
  67  private:
  68   Thread* _thread;
  69   int _level;
  70   GrowableArray<UnhandledOopEntry> *_oop_list;
  71   void allow_unhandled_oop(oop* op);
  72   void clear_unhandled_oops();
  73   UnhandledOops(Thread* thread);
  74   ~UnhandledOops();
  75 
  76  public:
  77   static void dump_oops(UnhandledOops* list);
  78   void register_unhandled_oop(oop* op, address pc);
  79   void unregister_unhandled_oop(oop* op);
  80 };
  81 
  82 #ifdef _LP64
  83 const intptr_t BAD_OOP_ADDR =  0xfffffffffffffff1;
  84 #else
  85 const intptr_t BAD_OOP_ADDR =  0xfffffff1;
  86 #endif // _LP64
  87 #endif // CHECK_UNHANDLED_OOPS
  88 
  89 #endif // SHARE_VM_RUNTIME_UNHANDLEDOOPS_HPP