Java bytecode fundamentals

Transcript

2. Java Bytecode Fundamentals JUG.LV 2011, Riga
3. whoami http://arhipov.blogspot.com @antonarhipov @javarebel Anton Arhipov ZeroTurnaround JRebel
4. who-are-you?
5. 1 + 2
6. 1 + 2 1 2 +
7. 1 + 2 1 2 + 1 2 +
8. 1 + 2 1 2 + 1 2 +
9. 1 + 2 1 2 + 1 2 + PUSH 1 1
10. 1 + 2 1 2 + 1 2 + PUSH 1 PUSH 2 2 1
11. 1 + 2 1 2 + 1 2 + PUSH 1 PUSH 2 ADD 3
12. 1 + 2 1 2 + 1 2 + ICONST_1 ICONST_2 IADD 3
13. ? = 1 + 2
14. Byte Code One-byte instructions 256 possible opcodes ~200 in use
15. Byte Code One-byte instructions 256 possible opcodes ~200 in use
17. The Master Plan javap Stack Machine Objects and Methods Flow Control
18. javap Java class file disassembler Used with no options shows class structure only Methods, superclass, interfaces, etc -c – shows the bytecode -private – shows all classes and members -s – prints internal types signatures -l – prints lines numbers and local variable tables
19. C:\work\jug\classes>javap Hello -c Compiled from "Hello.java" public class Hello extends java.lang.Object{ public Hello(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream; 3: ldc #3; //String Hello, World! 5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V
20. C:\work\jug\classes>javap Hello -verbose Compiled from "Hello.java“ public class Hello extends java.lang.Object SourceFile: "Hello.java" minor version: 0 major version: 50 Constant pool: const #1 = Method #6.#20; // java/lang/Object."<init>":()V const #2 = Field #21.#22; // java/lang/System.out:Ljava/io/PrintStream; const #3 = String #23; // Hello, World! const #4 = Method #24.#25; // java/io/PrintStream.println:(Ljava/lang/String;)V const #5 = class #26; // Hello const #6 = class #27; // java/lang/Object const #7 = Asciz <init>; const #8 = Asciz ()V;
21. C:\work\jug\classes>javap Hello -verbose … public Hello(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return LineNumberTable: line 1: 0 LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LHello;
22. C:\work\jug\classes>javap Hello -verbose … public static void main(java.lang.String[]); Code: Stack=2, Locals=1, Args_size=1 0: getstatic #2; //Field java/lang/System.out:Ljava/io/PrintStream; 3: ldc #3; //String Hello, World! 5: invokevirtual #4; //Method java/io/PrintStream.println:(Ljava/lang/String;)V 8: return LineNumberTable: line 4: 0 line 5: 8 LocalVariableTable: Start Length Slot Name Signature 0 9 0 args [Ljava/lang/String;
23. Stack Machine JVM is a stack-based machine Each thread has a stack Stack stores frames Frame is created on method invocation Frame: Operand stack Array of local variables
24. Frame
25. public java.lang.String getName(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: getfield #2; //Field name:Ljava/lang/String; 4: areturn LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LGet;
26. public java.lang.String getName(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: getfield #2; //Field name:Ljava/lang/String; 4: areturn LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LGet; aload_0 getfield 00 02 areturn 0 1 2 3 4
27. public java.lang.String getName(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: getfield #2; //Field name:Ljava/lang/String; 4: areturn LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LGet; 2A B4 00 02 B0 0 1 2 3 4
28. public java.lang.String getName(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: getfield #2; //Field name:Ljava/lang/String; 4: areturn LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LGet;
29. public java.lang.String getName(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: getfield #2; //Field name:Ljava/lang/String; 4: areturn LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LGet;
30. public java.lang.String getName(); Code: Stack=1, Locals=1, Args_size=1 0: aload_0 1: getfield #2; //Field name:Ljava/lang/String; 4: areturn LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LGet;
31. Stack Operations A B dup pop swap dup_x1 dup_x2
32. Stack Operations A B dup pop swap dup_x1 dup_x2 A
33. Stack Operations dup pop swap dup_x1 dup_x2 A B
34. Stack Operations dup pop swap dup_x1 dup_x2 A B
35. Stack Operations dup pop swap dup_x1 dup_x2 A B B
36. Stack Operations dup pop swap dup_x1 dup_x2 A B B B A
37. Local Variables
38. Local Variables public int calculate(int); Code: Stack=2, Locals=2, Args_size=2 … LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LLocalVariables; 0 5 1 value I
39. Local Variables public int calculate(int); Code: Stack=2, Locals=2, Args_size=2 … LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LLocalVariables; 0 5 1 value I
40. Local Variables public int calculate(int); Code: Stack=2, Locals=2, Args_size=2 … LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LLocalVariables; 0 5 1 value I
41. Local Variables public int calculate(int); Code: Stack=2, Locals=2, Args_size=2 … LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LLocalVariables; 0 5 1 value I The table maps numbers to names
42. Local Variables public int calculate(int); Code: Stack=2, Locals=2, Args_size=2 … LocalVariableTable: Start Length Slot Name Signature 0 5 0 this LLocalVariables; 0 5 1 value I Sized explicitly
43. Local Variables ldc "Hello" astore_0 iconst_1 astore_1 aload_0 depth value Stack var value Local Variables 0 1 2 3 4 0 1 2 3 4
44. Local Variables ldc "Hello" astore_0 iconst_1 astore_1 aload_0 depth value Stack var value Local Variables "Hello" 0 1 2 3 4 0 1 2 3 4
45. Local Variables ldc "Hello" astore_0 iconst_1 astore_1 aload_0 depth value Stack var value Local Variables "Hello" 0 1 2 3 4 0 1 2 3 4
46. Local Variables ldc "Hello" astore_0 iconst_1 astore_1 aload_0 depth value Stack var value Local Variables "Hello" 0 1 2 3 4 0 1 2 3 4 1
47. Local Variables ldc "Hello" astore_0 iconst_1 astore_1 aload_0 depth value Stack var value Local Variables "Hello" 0 1 2 3 4 0 1 2 3 4 1
48. Local Variables ldc "Hello" astore_0 iconst_1 astore_1 aload_0 depth value Stack var value Local Variables "Hello" 0 1 2 3 4 0 1 2 3 4 1 "Hello"
49. Local Variables & Stack Stack Local Variables Table store load
50. Object Initialization new <init> <clinit> Instance initialization method Class and interface initialization method
51. Object Initialization: static {} static {}; Code: 0: iconst_1 1: putstatic #2; //Field a:I 4: iconst_2 5: putstatic #3; //Field b:I 8: return
52. Object Initialization: static {} static {}; Code: 0: iconst_1 1: putstatic #2; //Field a:I 4: iconst_2 5: putstatic #3; //Field b:I 8: return <clinit>
53. Object Initialization: new public Initializer(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: aload_0 5: new #2; //class java/lang/Object 8: dup 9: invokespecial #1; //Method java/lang/Object."<init>":()V 12: putfield #3; //Field o:Ljava/lang/Object; 15: return
54. Object Initialization: new public Initializer(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: aload_0 5: new #2; //class java/lang/Object 8: dup 9: invokespecial #1; //Method java/lang/Object."<init>":()V 12: putfield #3; //Field o:Ljava/lang/Object; 15: return
55. Object Initialization: {}
56. Object Initialization: {}
57. Object Initialization: {} public Initializer(int); Code: 0: aload_0 1: invokespecial #1; // ..<init> 4: aload_0 5: iconst_1 6: putfield #2; //Field a:I 9: aload_0 10: iconst_2 11: putfield #3; //Field c:I 14: aload_0 15: iload_1 16: putfield #4; //Field b:I 19: return
58. Method Invocation invokestatic invokeinterface invokevirtual invokespecial invokedynamic
59. Parameter Passing
60. Parameter Passing parameter return value
61. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables Stack 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute();
62. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); this Stack
63. 0: aload_0 1: invokespecial #2; //createRandomValue() 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref Stack
64. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref Stack
65. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); this objectref Stack
66. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); this objectref objectref Stack
67. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; //incValue 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref objectref Stack
68. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; //incValue 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref objectref objectref Stack
69. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; //incValue 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; // Integer.intValue:() 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref objectref X Stack
70. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; //incValue 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref objectref 1 X Stack
71. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; //incValue 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref objectref X + 1 Stack
72. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; //incValue 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; //Integer.valueOf 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref objectref objectref Stack
73. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; //incValue 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref objectref objectref Stack
74. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref objectref Stack
75. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref Stack
76. 0: aload_0 1: invokespecial #2; 4: astore_1 5: aload_0 6: aload_1 7: invokespecial #3; 10: areturn depth value 1 2 3 4 5 6 1 2 3 var value Local Variables 1 2 3 var value 0: aload_1 1: invokevirtual #8; 4: iconst_1 5: iadd 6: invokestatic #7; 9: areturn private java.lang.Integer incValue(java.lang.Integer); public java.lang.Object execute(); objectref Stack
77. Flow Control
78. Flow Control GOTO
79. public int decide(int); Code: 0: iload_1 1: bipush 10 3: if_icmpge 8 6: iconst_0 7: ireturn 8: bipush 100 10: ireturn 1 2 3 depth value Stack
80. public int decide(int); Code: 0: iload_1 1: bipush 10 3: if_icmpge 8 6: iconst_0 7: ireturn 8: bipush 100 10: ireturn 1 2 3 depth value Stack a
81. public int decide(int); Code: 0: iload_1 1: bipush 10 3: if_icmpge 8 6: iconst_0 7: ireturn 8: bipush 100 10: ireturn 1 2 3 depth value Stack 10 a
82. public int decide(int); Code: 0: iload_1 1: bipush 10 3: if_icmpge 8 6: iconst_0 7: ireturn 8: bipush 100 10: ireturn 1 2 3 depth value Stack 10 a
83. public int decide(int); Code: 0: iload_1 1: bipush 10 3: if_icmpge 8 6: iconst_0 7: ireturn 8: bipush 100 10: ireturn 1 2 3 depth value Stack
84. public int decide(int); Code: 0: iload_1 1: bipush 10 3: if_icmpge 8 6: iconst_0 7: ireturn 8: bipush 100 10: ireturn 1 2 3 depth value Stack 100
85. public int decide(int); Code: 0: iload_1 1: bipush 10 3: if_icmpge 8 6: iconst_0 7: ireturn 8: bipush 100 10: ireturn 1 2 3 depth value Stack 100
86. public int decide(int); Code: 0: iload_1 1: bipush 10 3: if_icmpge 8 6: iconst_0 7: ireturn 8: bipush 100 10: ireturn 1 2 3 depth value Stack
87. ant.arhipov@gmail.com http://arhipov.blogspot.com @antonarhipov @javarebel