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 rax, 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 #ifdef WIN32

    90   // Expecting to be called with "thiscall" conventions -- the arguments

    91   // are on the stack, except that the "this" pointer is in rcx.

    92 #else

    93   // Expecting to be called with Unix conventions -- the arguments

    94   // are on the stack, including the "this" pointer.

    95 #endif

    96 

    97   // In addition, rax was set (above) to the offset of the method in the

    98   // table.

    99 

   100 #ifdef WIN32

   101   __ push(rcx);                         // save "this"

   102 #endif

   103   __ mov(rcx, rax);

   104   __ shrptr(rcx, 8);                    // isolate vtable identifier.

   105   __ shlptr(rcx, LogBytesPerWord);

   106   Address index(noreg, rcx,  Address::times_1);

   107   ExternalAddress vtbl((address)vtbl_list);

   108   __ movptr(rdx, ArrayAddress(vtbl, index)); // get correct vtable address.

   109 #ifdef WIN32

   110   __ pop(rcx);                          // restore "this"

   111 #else

   112   __ movptr(rcx, Address(rsp, BytesPerWord));   // fetch "this"

   113 #endif

   114   __ movptr(Address(rcx, 0), rdx);      // update vtable pointer.

   115 

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

   117   __ shlptr(rax, LogBytesPerWord);

   118   __ addptr(rax, rdx);                  // address of real method pointer.

   119   __ jmp(Address(rax, 0));              // get real method pointer.

   120 

   121   __ flush();

   122 

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

   124 }