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
generate_vtable_methods(void ** vtbl_list,void ** vtable,char ** md_top,char * md_end,char ** mc_top,char * mc_end)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 }
115