1 /*

     2  * Copyright (c) 2004, 2012, 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 #include "precompiled.hpp"

    26 #include "asm/macroAssembler.hpp"

    27 #include "asm/codeBuffer.hpp"

    28 #include "memory/metaspaceShared.hpp"

    29 

    30 // Generate the self-patching vtable method:

    31 //

    32 // This method will be called (as any other Klass virtual method) with

    33 // the Klass itself as the first argument.  Example:

    34 //

    35 //      oop obj;

    36 //      int size = obj->klass()->oop_size(this);

    37 //

    38 // for which the virtual method call is Klass::oop_size();

    39 //

    40 // The dummy method is called with the Klass object as the first

    41 // operand, and an object as the second argument.

    42 //

    43 

    44 //=====================================================================

    45 

    46 // All of the dummy methods in the vtable are essentially identical,

    47 // differing only by an ordinal constant, and they bear no relationship

    48 // to the original method which the caller intended. Also, there needs

    49 // to be 'vtbl_list_size' instances of the vtable in order to

    50 // differentiate between the 'vtable_list_size' original Klass objects.

    51 

    52 #define __ masm->

    53 

    54 void MetaspaceShared::generate_vtable_methods(void** vtbl_list,

    55                                                    void** vtable,

    56                                                    char** md_top,

    57                                                    char* md_end,

    58                                                    char** mc_top,

    59                                                    char* mc_end) {

    60 

    61   intptr_t vtable_bytes = (num_virtuals * vtbl_list_size) * sizeof(void*);

    62   *(intptr_t *)(*md_top) = vtable_bytes;

    63   *md_top += sizeof(intptr_t);

    64   void** dummy_vtable = (void**)*md_top;

    65   *vtable = dummy_vtable;

    66   *md_top += vtable_bytes;

    67 

    68   // Get ready to generate dummy methods.

    69 

    70   CodeBuffer cb((unsigned char*)*mc_top, mc_end - *mc_top);

    71   MacroAssembler* masm = new MacroAssembler(&cb);

    72 

    73   Label common_code;

    74   for (int i = 0; i < vtbl_list_size; ++i) {

    75     for (int j = 0; j < num_virtuals; ++j) {

    76       dummy_vtable[num_virtuals * i + j] = (void*)masm->pc();

    77 

    78       // Load eax with a value indicating vtable/offset pair.

    79       // -- bits[ 7..0]  (8 bits) which virtual method in table?

    80       // -- bits[12..8]  (5 bits) which virtual method table?

    81       // -- must fit in 13-bit instruction immediate field.

    82       __ movl(rax, (i << 8) + j);

    83       __ jmp(common_code);

    84     }

    85   }

    86 

    87   __ bind(common_code);

    88 

    89   // Expecting to be called with "thiscall" convections -- the arguments

    90   // are on the stack and the "this" pointer is in c_rarg0. In addition, rax

    91   // was set (above) to the offset of the method in the table.

    92 

    93   __ push(c_rarg1);                     // save & free register

    94   __ push(c_rarg0);                     // save "this"

    95   __ mov(c_rarg0, rax);

    96   __ shrptr(c_rarg0, 8);                // isolate vtable identifier.

    97   __ shlptr(c_rarg0, LogBytesPerWord);

    98   __ lea(c_rarg1, ExternalAddress((address)vtbl_list)); // ptr to correct vtable list.

    99   __ addptr(c_rarg1, c_rarg0);          // ptr to list entry.

   100   __ movptr(c_rarg1, Address(c_rarg1, 0));      // get correct vtable address.

   101   __ pop(c_rarg0);                      // restore "this"

   102   __ movptr(Address(c_rarg0, 0), c_rarg1);      // update vtable pointer.

   103 

   104   __ andptr(rax, 0x00ff);                       // isolate vtable method index

   105   __ shlptr(rax, LogBytesPerWord);

   106   __ addptr(rax, c_rarg1);              // address of real method pointer.

   107   __ pop(c_rarg1);                      // restore register.

   108   __ movptr(rax, Address(rax, 0));      // get real method pointer.

   109   __ jmp(rax);                          // jump to the real method.

   110 

   111   __ flush();

   112 

   113   *mc_top = (char*)__ pc();

   114 }