running jvmti agent in linux
Tags: java
Published: 2023-12-17 21:43:39

I was trying to answer https://stackoverflow.com/questions/5751492/jvmti-agent-never-returns-the-thread-state-terminated which is related agentlib and jvmti, as a senior java engineer and have been working with java professionally since 2006, never tried jvmti. 

So found a small example here https://github.com/sachin-handiekar/jvmti-examples which is not showing how to run it, so I manage to figure that out and note it here as blog, in case someone else would like to see how jvmti called in linux

1. Compiling the cpp side we use cmake and make like below
```shell
oz-mint@ozmint-MACH-WX9:~/tmp/jvmti-examples/GetAllStackTraces/Native$ cmake CMakeLists.txt 
-- The C compiler identification is GNU 11.4.0
-- The CXX compiler identification is GNU 11.4.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found JNI: /home/oz-mint/.sdkman/candidates/java/current/lib/libjawt.so  
-- JNI_INCLUDE_DIRS=/home/oz-mint/.sdkman/candidates/java/current/include;/home/oz-mint/.sdkman/candidates/java/current/include/linux;/home/oz-mint/.sdkman/candidates/java/current/include
-- JNI_LIBRARIES=/home/oz-mint/.sdkman/candidates/java/current/lib/libjawt.so;/home/oz-mint/.sdkman/candidates/java/current/lib/server/libjvm.so
-- Configuring done
-- Generating done
-- Build files have been written to: /home/oz-mint/tmp/jvmti-examples/GetAllStackTraces/Native
oz-mint@ozmint-MACH-WX9:~/tmp/jvmti-examples/GetAllStackTraces/Native$ make
[ 50%] Building CXX object CMakeFiles/GetAllStackTraces.dir/library.cpp.o
[100%] Linking CXX shared library libGetAllStackTraces.so
[100%] Built target GetAllStackTraces
```
2. For compiling the java class we need to use -g 
*/jvmti-examples/GetAllStackTraces/Java/src$ javac -g GetAllStackTracesTest.java*
3. Running the java class with the agentlib so command and result below
```shell
oz-mint@ozmint-MACH-WX9:~/tmp/jvmti-examples/GetAllStackTraces/Java/src$ java -agentpath:../../Native/libGetAllStackTraces.so -agentlib:GetAllStackTraces GetAllStackTracesTest 

 Class Name : LGetAllStackTracesTest;
 Got Exception in Method : exceptionMethod
 Class Name : LGetAllStackTracesTest;
 Got Exception in Method : methodStack5
 Class Name : LGetAllStackTracesTest;
 Got Exception in Method : methodStack4
 Class Name : LGetAllStackTracesTest;
 Got Exception in Method : methodStack3
 Class Name : LGetAllStackTracesTest;
 Got Exception in Method : methodStack2
 Class Name : LGetAllStackTracesTest;
 Got Exception in Method : exceptionMethod
 Class Name : LGetAllStackTracesTest;
 Got Exception in Method : methodStack5
 Class Name : LGetAllStackTracesTest;
 Got Exception in Method : methodStack4
 Class Name : LGetAllStackTracesTest;
 Got Exception in Method : methodStack3
 Class Name : LGetAllStackTracesTest;
Exception thrown in Java code...
 Got Exception in Method : methodStack2oz-mint@ozmint-MACH-WX9:~/tmp/jvmti-examples/GetAllStackTraces/Java/src$ 
```
Ref:https://www.oracle.com/technical-resources/articles/javase/jvmti.html