1 /*
   2  * Copyright (c) 1997, 2018, 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_CODE_VTABLESTUBS_HPP
  26 #define SHARE_VM_CODE_VTABLESTUBS_HPP
  27 
  28 #include "code/vmreg.hpp"
  29 #include "memory/allocation.hpp"
  30 
  31 // A VtableStub holds an individual code stub for a pair (vtable index, #args) for either itables or vtables
  32 // There's a one-to-one relationship between a VtableStub and such a pair.
  33 
  34 class VtableStub {
  35  private:
  36   friend class VtableStubs;
  37 
  38   static address _chunk;             // For allocation
  39   static address _chunk_end;         // For allocation
  40   static VMReg   _receiver_location; // Where to find receiver
  41 
  42   VtableStub*    _next;              // Pointer to next entry in hash table
  43   const short    _index;             // vtable index
  44   short          _ame_offset;        // Where an AbstractMethodError might occur
  45   short          _npe_offset;        // Where a NullPointerException might occur
  46   bool           _is_vtable_stub;    // True if vtable stub, false, is itable stub
  47   /* code follows here */            // The vtableStub code
  48 
  49   void* operator new(size_t size, int code_size) throw();
  50 
  51   VtableStub(bool is_vtable_stub, int index)
  52         : _next(NULL), _is_vtable_stub(is_vtable_stub),
  53           _index(index), _ame_offset(-1), _npe_offset(-1) {}
  54   VtableStub* next() const                       { return _next; }
  55   int index() const                              { return _index; }
  56   static VMReg receiver_location()               { return _receiver_location; }
  57   void set_next(VtableStub* n)                   { _next = n; }
  58 
  59  public:
  60   address code_begin() const                     { return (address)(this + 1); }
  61   address code_end() const                       { return code_begin() + pd_code_size_limit(_is_vtable_stub); }
  62   address entry_point() const                    { return code_begin(); }
  63   static int entry_offset()                      { return sizeof(class VtableStub); }
  64 
  65   bool matches(bool is_vtable_stub, int index) const {
  66     return _index == index && _is_vtable_stub == is_vtable_stub;
  67   }
  68   bool contains(address pc) const                { return code_begin() <= pc && pc < code_end(); }
  69 
  70  private:
  71   void set_exception_points(address npe_addr, address ame_addr) {
  72     _npe_offset = npe_addr - code_begin();
  73     _ame_offset = ame_addr - code_begin();
  74     assert(is_abstract_method_error(ame_addr),   "offset must be correct");
  75     assert(is_null_pointer_exception(npe_addr),  "offset must be correct");
  76     assert(!is_abstract_method_error(npe_addr),  "offset must be correct");
  77     assert(!is_null_pointer_exception(ame_addr), "offset must be correct");
  78   }
  79 
  80   // platform-dependent routines
  81   static int  pd_code_size_limit(bool is_vtable_stub);
  82   static int  pd_code_alignment();
  83   // CNC: Removed because vtable stubs are now made with an ideal graph
  84   // static bool pd_disregard_arg_size();
  85 
  86   static void align_chunk() {
  87     uintptr_t off = (uintptr_t)( _chunk + sizeof(VtableStub) ) % pd_code_alignment();
  88     if (off != 0)  _chunk += pd_code_alignment() - off;
  89   }
  90 
  91  public:
  92   // Query
  93   bool is_itable_stub()                          { return !_is_vtable_stub; }
  94   bool is_vtable_stub()                          { return  _is_vtable_stub; }
  95   bool is_abstract_method_error(address epc)     { return epc == code_begin()+_ame_offset; }
  96   bool is_null_pointer_exception(address epc)    { return epc == code_begin()+_npe_offset; }
  97 
  98   void print_on(outputStream* st) const;
  99   void print() const                             { print_on(tty); }
 100 
 101 };
 102 
 103 
 104 // VtableStubs creates the code stubs for compiled calls through vtables.
 105 // There is one stub per (vtable index, args_size) pair, and the stubs are
 106 // never deallocated. They don't need to be GCed because they contain no oops.
 107 
 108 class VtableStubs : AllStatic {
 109  public:                                         // N must be public (some compilers need this for _table)
 110   enum {
 111     N    = 256,                                  // size of stub table; must be power of two
 112     mask = N - 1
 113   };
 114 
 115  private:
 116   static VtableStub* _table[N];                  // table of existing stubs
 117   static int         _number_of_vtable_stubs;    // number of stubs created so far (for statistics)
 118 
 119   static VtableStub* create_vtable_stub(int vtable_index);
 120   static VtableStub* create_itable_stub(int vtable_index);
 121   static VtableStub* lookup            (bool is_vtable_stub, int vtable_index);
 122   static void        enter             (bool is_vtable_stub, int vtable_index, VtableStub* s);
 123   static inline uint hash              (bool is_vtable_stub, int vtable_index);
 124   static address     find_stub         (bool is_vtable_stub, int vtable_index);
 125 
 126  public:
 127   static address     find_vtable_stub(int vtable_index) { return find_stub(true,  vtable_index); }
 128   static address     find_itable_stub(int itable_index) { return find_stub(false, itable_index); }
 129   static VtableStub* entry_point(address pc);                        // vtable stub entry point for a pc
 130   static bool        contains(address pc);                           // is pc within any stub?
 131   static VtableStub* stub_containing(address pc);                    // stub containing pc or NULL
 132   static int         number_of_vtable_stubs() { return _number_of_vtable_stubs; }
 133   static void        initialize();
 134   static void        vtable_stub_do(void f(VtableStub*));            // iterates over all vtable stubs
 135 };
 136 
 137 #endif // SHARE_VM_CODE_VTABLESTUBS_HPP
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