1 /* 2 * Copyright (c) 2005, 2019, 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_RUNTIME_UNHANDLEDOOPS_HPP 26 #define SHARE_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 public: oop_ptr()57 oop* oop_ptr() { return _oop_ptr; } UnhandledOopEntry()58 UnhandledOopEntry() : _oop_ptr(NULL), _ok_for_gc(false) {} UnhandledOopEntry(oop * op)59 UnhandledOopEntry(oop* op) : 60 _oop_ptr(op), _ok_for_gc(false) {} 61 }; 62 63 64 class UnhandledOops : public CHeapObj<mtThread> { 65 friend class Thread; 66 private: 67 Thread* _thread; 68 int _level; 69 GrowableArray<UnhandledOopEntry> *_oop_list; 70 void allow_unhandled_oop(oop* op); 71 void clear_unhandled_oops(); 72 UnhandledOops(Thread* thread); 73 ~UnhandledOops(); 74 75 public: 76 static void dump_oops(UnhandledOops* list); 77 void register_unhandled_oop(oop* op); 78 void unregister_unhandled_oop(oop* op); 79 }; 80 81 #ifdef _LP64 82 const intptr_t BAD_OOP_ADDR = 0xfffffffffffffff1; 83 #else 84 const intptr_t BAD_OOP_ADDR = 0xfffffff1; 85 #endif // _LP64 86 #endif // CHECK_UNHANDLED_OOPS 87 88 #endif // SHARE_RUNTIME_UNHANDLEDOOPS_HPP 89