local_jstack

Thread dump like jstack in local JVM process (not interprocess like jstack in jdk) by dirty JNI way.

在本地 JVM 进程（而不是jdk中jstack的进程间）中通过粗糙的 JNI 方式进行类似 jstack 的线程转储

支持的平台 Supported Platform

• linux x64
• macos x64
• windows x64

上手 Get Started

1. 首先找到JRE环境的libjvm.so中的thread_dump(AttachOperation*, outputStream*)函数的偏移量

   • unix平台，以21.0.5-ms为例，为4892880：

     $ nm -t d -C /usr/local/sdkman/candidates/java/21.0.5-ms/lib/server/libjvm.so |grep -F 'thread_dump(AttachOperation*, outputStream*)'
     0000000004892880 t thread_dump(AttachOperation*, outputStream*)

   • Windows平台，则需要借助map文件来获取函数偏移量，例如microsoft-jdk-21.0.3-windows-x64.zip，需要下载微软提供的调试信息microsoft-jdk-debugsymbols-21.0.3-windows-x64.zip，然后解压调试信息

     首先是获取ImageBase，如下命令的结果第三列0000000180000000就是ImageBase的Rva+Base 16进制形式：

     findstr "__ImageBase" C:\jdk-21.0.3+9-debug-symbols\bin\server\jvm.dll.map
      0000:00000000       __ImageBase                0000000180000000     <linker-defined>
     

     再是获取thread_dump(AttachOperation*, outputStream*)方法在dll中的地址，如下命令的结果第三列00000001801315e0就是thread_dump函数Rva+Base16进制形式：

     findstr "?thread_dump@@YAJPEAVAttachOperation@@PEAVoutputStream@@@Z" C:\jdk-21.0.3+9-debug-symbols\bin\server\jvm.dll.map | findstr /V unwind
      0001:001305e0       ?thread_dump@@YAJPEAVAttachOperation@@PEAVoutputStream@@@Z 00000001801315e0 f   attachListener.obj

     然后两者做减法：00000001801315e0 - 0000000180000000的结果1315e0就是thread_dump函数在jvm.dll中的偏移量

2. 使用java.io.Writer来承接线程栈

   import java.io.StringWriter;
   
   public class MyApp {
       public static void main(String[] args) {
           StringWriter writer = new StringWriter();;
           LocalJStack.dumpStack(writer);
           System.out.println(writer);
       }
   }

3. 编译、运行

   $ javac -cp localjstack-0.0.1.jar MyApp.java
   $ /usr/local/sdkman/candidates/java/21.0.5-ms/bin/java -Dlocaljstack.threadDumpOffset=4892880 -cp localjstack-0.0.1.jar:. MyApp
   

   打印到标准输出:

   2025-02-19 14:58:09
   Full thread dump OpenJDK 64-Bit Server VM (21.0.5+11-LTS mixed mode, sharing):
   
   Threads class SMR info:
   _java_thread_list=0x000077b8f415e3b0, length=10, elements={
   ...
   

   如果使用Maven，在pom.xml中添加本项目:

   <dependency>
       <groupId>app</groupId>
       <artifactId>localjstack</artifactId>
       <version>0.0.1</version>
   </dependency>

编译源代码 Build From Source

$ cmake --build ./build --config Debug --target LibLocalJStack -j 4 --
$ mvn package

产出jar包为target/localjstack-0.0.1.jar