1 /*
2  * Copyright (c) 2004, 2011, Oracle and/or its affiliates. All rights reserved.
3  *
4  * Redistribution and use in source and binary forms, with or without
5  * modification, are permitted provided that the following conditions
6  * are met:
7  *
8  *   - Redistributions of source code must retain the above copyright
9  *     notice, this list of conditions and the following disclaimer.
10  *
11  *   - Redistributions in binary form must reproduce the above copyright
12  *     notice, this list of conditions and the following disclaimer in the
13  *     documentation and/or other materials provided with the distribution.
14  *
15  *   - Neither the name of Oracle nor the names of its
16  *     contributors may be used to endorse or promote products derived
17  *     from this software without specific prior written permission.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
20  * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
24  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
25  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
26  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
27  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
28  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
29  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30  */
31 
32 /*
33  * This source code is provided to illustrate the usage of a given feature
34  * or technique and has been deliberately simplified. Additional steps
35  * required for a production-quality application, such as security checks,
36  * input validation and proper error handling, might not be present in
37  * this sample code.
38  */
39 
40 
41 
42 /* Java class to hold static methods which will be called in byte code
43  *    injections of all class files.
44  */
45 
46 public class Mtrace {
47 
48     /* Master switch that activates methods. */
49 
50     private static int engaged = 0;
51 
52     /* At the very beginning of every method, a call to method_entry()
53      *     is injected.
54      */
55 
_method_entry(Object thr, int cnum, int mnum)56     private static native void _method_entry(Object thr, int cnum, int mnum);
method_entry(int cnum, int mnum)57     public static void method_entry(int cnum, int mnum)
58     {
59         if ( engaged != 0 ) {
60             _method_entry(Thread.currentThread(), cnum, mnum);
61         }
62     }
63 
64     /* Before any of the return bytecodes, a call to method_exit()
65      *     is injected.
66      */
67 
_method_exit(Object thr, int cnum, int mnum)68     private static native void _method_exit(Object thr, int cnum, int mnum);
method_exit(int cnum, int mnum)69     public static void method_exit(int cnum, int mnum)
70     {
71         if ( engaged != 0 ) {
72             _method_exit(Thread.currentThread(), cnum, mnum);
73         }
74     }
75 
76 }
77