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https://github.com/rapilab/jvm.rust
Learning rust for build a simple jvm
https://github.com/rapilab/jvm.rust
Last synced: 5 days ago
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Learning rust for build a simple jvm
- Host: GitHub
- URL: https://github.com/rapilab/jvm.rust
- Owner: rapilab
- Created: 2020-07-14T06:15:25.000Z (over 4 years ago)
- Default Branch: master
- Last Pushed: 2020-07-16T07:52:30.000Z (over 4 years ago)
- Last Synced: 2024-08-03T09:12:26.717Z (4 months ago)
- Language: Rust
- Size: 244 KB
- Stars: 9
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# Rust + JVM research
## Roadmap
- [x] .class parser
- [ ] code parser
- [x] support hello world
- [ ] VM
- [ ] Runtime
- [ ] Thread
- [ ] Frame
- [ ] JIT / interp
- [ ] GC
- [ ] _Pass test cases in JDK_
## Document
### .class file Parser
- Official：[Java The class File Format ](https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html)
- 中文相关翻译：[JVM 揭秘：一个 class 文件的前世今生](https://zhuanlan.zhihu.com/p/33440868)
#### The ClassFile Structure
```
ClassFile {
u4 magic;
u2 minor_version;
u2 major_version;
u2 constant_pool_count;
cp_info constant_pool[constant_pool_count-1];
u2 access_flags;
u2 this_class;
u2 super_class;
u2 interfaces_count;
u2 interfaces[interfaces_count];
u2 fields_count;
field_info fields[fields_count];
u2 methods_count;
method_info methods[methods_count];
u2 attributes_count;
attribute_info attributes[attributes_count];
}
```
## Tools
### HSDB
> HSDB（Hotspot Debugger），是一款内置于 SA 中的GUI调试工具，集成了各种JVM 监控工具，适用于深入分析JVM的内部状态
```bash
java -cp sa-jdi.jar sun.jvm.hotspot.HSDB
```
or
```bash
sudo java -classpath "$JAVA_HOME/lib/sa-jdi.jar" sun.jvm.hotspot.HSDB
```
### Hex 显示
Vim show bytes:
```
:%!xxd
```
with Command line
```
xxd filename | less
```
hex examples:
```
00000000: cafe babe 0000 0034 0022 0a00 0600 1409 .......4."......
00000010: 0015 0016 0800 170a 0018 0019 0700 1a07 ................
00000020: 001b 0100 063c 696e 6974 3e01 0003 2829 ........()
00000030: 5601 0004 436f 6465 0100 0f4c 696e 654e V...Code...LineN
00000040: 756d 6265 7254 6162 6c65 0100 124c 6f63 umberTable...Loc
00000050: 616c 5661 7269 6162 6c65 5461 626c 6501 alVariableTable.
00000060: 0004 7468 6973 0100 0c4c 4865 6c6c 6f57 ..this...LHelloW
00000070: 6f72 6c64 3b01 0004 6d61 696e 0100 1628 orld;...main...(
00000080: 5b4c 6a61 7661 2f6c 616e 672f 5374 7269 [Ljava/lang/Stri
00000090: 6e67 3b29 5601 0004 6172 6773 0100 135b ng;)V...args...[
000000a0: 4c6a 6176 612f 6c61 6e67 2f53 7472 696e Ljava/lang/Strin
000000b0: 673b 0100 0a53 6f75 7263 6546 696c 6501 g;...SourceFile.
000000c0: 000f 4865 6c6c 6f57 6f72 6c64 2e6a 6176 ..HelloWorld.jav
000000d0: 610c 0007 0008 0700 1c0c 001d 001e 0100 a...............
000000e0: 0d48 656c 6c6f 2c20 776f 726c 6421 0700 .Hello, world!..
000000f0: 1f0c 0020 0021 0100 0a48 656c 6c6f 576f ... .!...HelloWo
00000100: 726c 6401 0010 6a61 7661 2f6c 616e 672f rld...java/lang/
00000110: 4f62 6a65 6374 0100 106a 6176 612f 6c61 Object...java/la
00000120: 6e67 2f53 7973 7465 6d01 0003 6f75 7401 ng/System...out.
00000130: 0015 4c6a 6176 612f 696f 2f50 7269 6e74 ..Ljava/io/Print
00000140: 5374 7265 616d 3b01 0013 6a61 7661 2f69 Stream;...java/i
00000150: 6f2f 5072 696e 7453 7472 6561 6d01 0007 o/PrintStream...
00000160: 7072 696e 746c 6e01 0015 284c 6a61 7661 println...(Ljava
00000170: 2f6c 616e 672f 5374 7269 6e67 3b29 5600 /lang/String;)V.
00000180: 2100 0500 0600 0000 0000 0200 0100 0700 !...............
00000190: 0800 0100 0900 0000 2f00 0100 0100 0000 ......../.......
000001a0: 052a b700 01b1 0000 0002 000a 0000 0006 .*..............
000001b0: 0001 0000 0001 000b 0000 000c 0001 0000 ................
000001c0: 0005 000c 000d 0000 0009 000e 000f 0001 ................
000001d0: 0009 0000 0037 0002 0001 0000 0009 b200 .....7..........
000001e0: 0212 03b6 0004 b100 0000 0200 0a00 0000 ................
000001f0: 0a00 0200 0000 0400 0800 0500 0b00 0000 ................
00000200: 0c00 0100 0000 0900 1000 1100 0000 0100 ................
00000210: 1200 0000 0200 13 .......
```
### javap
```
javap -verbose testdata.java8.HelloWorld
```
```
Warning: Binary file testdata.java8.HelloWorld contains HelloWorld
Classfile /Users/fdhuang/learn/learn-rust/jvm/testdata/java8/HelloWorld.class
Last modified Jul 10, 2020; size 535 bytes
MD5 checksum 68b4c9f255e18ce561bb5d980f7523c0
Compiled from "HelloWorld.java"
public class HelloWorld
minor version: 0
major version: 52
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #6.#20 // java/lang/Object."":()V
#2 = Fieldref #21.#22 // java/lang/System.out:Ljava/io/PrintStream;
#3 = String #23 // Hello, world!
#4 = Methodref #24.#25 // java/io/PrintStream.println:(Ljava/lang/String;)V
#5 = Class #26 // HelloWorld
#6 = Class #27 // java/lang/Object
#7 = Utf8
#8 = Utf8 ()V
#9 = Utf8 Code
#10 = Utf8 LineNumberTable
#11 = Utf8 LocalVariableTable
#12 = Utf8 this
#13 = Utf8 LHelloWorld;
#14 = Utf8 main
#15 = Utf8 ([Ljava/lang/String;)V
#16 = Utf8 args
#17 = Utf8 [Ljava/lang/String;
#18 = Utf8 SourceFile
#19 = Utf8 HelloWorld.java
#20 = NameAndType #7:#8 // "":()V
#21 = Class #28 // java/lang/System
#22 = NameAndType #29:#30 // out:Ljava/io/PrintStream;
#23 = Utf8 Hello, world!
#24 = Class #31 // java/io/PrintStream
#25 = NameAndType #32:#33 // println:(Ljava/lang/String;)V
#26 = Utf8 HelloWorld
#27 = Utf8 java/lang/Object
#28 = Utf8 java/lang/System
#29 = Utf8 out
#30 = Utf8 Ljava/io/PrintStream;
#31 = Utf8 java/io/PrintStream
#32 = Utf8 println
#33 = Utf8 (Ljava/lang/String;)V
{
public HelloWorld();
descriptor: ()V
flags: ACC_PUBLIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokespecial #1 // Method java/lang/Object."":()V
4: return
LineNumberTable:
line 1: 0
LocalVariableTable:
Start Length Slot Name Signature
0 5 0 this LHelloWorld;
public static void main(java.lang.String[]);
descriptor: ([Ljava/lang/String;)V
flags: ACC_PUBLIC, ACC_STATIC
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;
}
SourceFile: "HelloWorld.java"
```
### Run Results
Method 1:
```
ALOAD_0
INVOKESPECIAL
NOP
ACONST_NULL
RETURN
```
Method 2:
```
GETSTATIC
NOP
ICONST_M1
LDC
ICONST_0
INVOKEVIRTUAL
NOP
ICONST_1
RETURN
```
### OpCode
Wiki: [Java OpCode](https://en.wikipedia.org/wiki/Java_bytecode_instruction_listings)
HelloWorld 相关
| 常量池操作 | 含义 |
|---|---|
| GETSTATIC | 获取类的静态字段，将其值压入栈顶 |
| ICONST_M1 | int 型常量 -1 进栈|
| LDC | int、float 或 String 型常量从常量池推送至栈顶|
| ICONST_0 | int 型常量 0 进栈 |
| INVOKEVIRTUAL | 调用实例方法 - 虚方法分派 |
| ICONST_1 | int 型常量 1 进栈 |
## 编译器
- 前端编译器： JDK 的 javac、Eclipse JDT 中的 ECJ
- 即时编译器（JIT）： HotSpot 虚拟机中的 C1、C2 编译器，Graal 编译器
- 运行时编译器（AOT）： JDK 的 Jaotc、GNU Compiler for the Java、Excelsior JET
### JVM Runtime
Thread
- PC (Program Counter)
- Stack
- Frame
- Return Value
- Local Vars
- Operand Stack
- Current Class Constant Pool Ref
### Type Descriptor
```
[Z = boolean
[B = byte
[S = short
[I = int
[J = long
[F = float
[D = double
[C = char
[L = any non-primitives(Object)
```
## Related
- Go -> [https://github.com/zxh0/jvm.go](https://github.com/zxh0/jvm.go) 3.1k stars
- Rust -> [https://github.com/douchuan/jvm](https://github.com/douchuan/jvm) 278 stars
- Rust -> [ocelotter](https://github.com/kittylyst/ocelotter) 45 stars
## process
### Java.c
#### 虚拟机生命周期
Launcher:
- OSLauncher -> OSLauncher::launch
- AppLauncher::launchApp
- AppLauncher::createJvmLauncher
- JVMLauncher::initFromConfigFile
- JVMLauncher::launch
#### Thread
- Threads::create_vm
-
#### 主线程
```c++
// src/java.base/share/native/libjli/java.c
1. 初始化虚拟机
RegisterThread();
InitializeJVM();
FreeKnownVMs();
2. 获取应用程序主类
mainClass = LoadMainClass(env, mode, what);
3. 获取应用程序主方法
appClass = GetApplicationClass(env);
mainArgs = CreateApplicationArgs(env, argv, argc);
PostJVMInit(env, appClass, vm);
mainID = (*env)->GetStaticMethodID(env, mainClass, "main",
"([Ljava/lang/String;)V");
4. 传递应用程序参数并执行主方法
(*env)->CallStaticVoidMethod(env, mainClass, mainID, mainArgs);
5. Detach 主线程
(*vm)->DetachCurrentThread(vm)
6. 销毁 JVM
(*vm)->DestroyJavaVM(vm);
```
### Thread
[探秘 JVM 内部结构](https://wu-sheng.github.io/me/articles/JVMInternals.html)
#### Program Counter (PC)
当前操作指令或opcode的地址指针，如果当前方法是本地方法，则PC值为undefined。每个CPU都有一个PC，一般来说，每一次指令之后，PC值会增加，指向下一个操作指令的地址。JVM使用PC保持操作指令的执行顺序，PC值实际上就是指向方法区(Method Area)中的内存地址。
#### Stack
每一个线程都拥有自己的栈（Stack），用于在本线程中正在执行的方法。栈是一个先进后出（LIFO）的数据结构，所以当前的执行方法位于栈顶。每一个方法开始执行时，一个新的帧（Frame)被创建（压栈），并添加到栈顶。当方法正常执行返回，或方法执行时抛出一个未捕获的异常，则此帧被移除（弹栈）。栈，除了压栈和弹栈操作外，不会被执行操作，因此，帧对象可以被分配在堆（Heap）内存中，并且不需要分配连续内存。