Interest in Java based attach provider implementation?

[Magnus Ihse Bursie]

Hi Philippe,

There is an ongoing effort about "Panamization" (that is, adapting it to 
use FFM instead of JNI) of native code in the JDK in general. This is 
discussed on the core-libs-dev mailing list. I've cc:ed them. I think it 
would be beneficial if you coordinate your efforts with the Panamization 
effort.

/Magnus


On 2025-06-15 17:43, Philippe Marschall wrote:
> Hello
>
> I further pursued the approach
>
> - Rebased the Linux implementation [1], implemented the permission 
> check using JSR 203 and the Unix domain sockets using JEP 380.
> - Applied the same changes to the AIX implementation [2].
> - Switched Linux to an FFM based kill implementation [3], completely 
> getting rid of JNI.
> -  Updated the macOS implementation [4], implemented the permission 
> check using JSR 203 and the Unix domain sockets using JEP 380.
> - Switched macOS to an FFM based kill and sysctl implementation [5], 
> completely getting rid of JNI.
>
> I ran the serviceability test suite on Linux and macOS and it passes. 
> I manually verified that I can attach to JVMs using local builds.
>
> I could not test on AIX.
>
>  [1] 
> https://github.com/marschall/jdk/commit/3a7796daadad7c9d2d85e9e4623f170baecc0e41
>  [2] 
> https://github.com/marschall/jdk/commit/962729e0bfb6b7d86af303f25c6670d407d1d2d9
>  [3] 
> https://github.com/marschall/jdk/commit/7b5f1bf6f55458a7f69f50b8fdf4986e22202559
>  [4] 
> https://github.com/marschall/jdk/commit/93372a124eca6078fde5597c2498b381a4ef5dfa
>  [5] 
> https://github.com/marschall/jdk/commit/c5faf9655bbb85cc3ed9b2a7ef15b08ab83d1d8b
>
> Cheers
> Philippe
>
> On 20.04.22 22:13, Philippe Marschall wrote:
>> Hello
>>
>> I hope this is the right mailing list. I recently had a look at the
>> Linux attach provider implementation and could not help but noticing
>> that a large part, if not all of it, could be replaced with Java.
>> Besides getting rid of the C code this should allow us to unify the AIX,
>> Linux and macOS implementations under a single Unix implementation.
>>
>> The permission check can be implemented using JSR 203 [1] to access uid,
>> gid and file mode and using jdk.internal.misc.VM to get the euid and 
>> egid.
>>
>> Reading and writing to Unix domain sockets can be done through JEP 
>> 380 [2].
>>
>> Sending SIGQUIT to a process could in theory done through JEP 102 [3]
>> however sending SIGQUIT to self is currently blocked. This is required
>> for the self attach mechanism. There a very small C function is still
>> needed for now, this is hopefully portable.
>>
>> I did a small prototype [4]. The tier1 suite runs and I can attach to a
>> local JVM.
>>
>> The overhead will likely be a bit higher as we go through more JDK
>> abstractions.
>>
>>   [1] https://jcp.org/en/jsr/detail?id=203
>>   [2] https://openjdk.java.net/jeps/380
>>   [3] https://openjdk.java.net/jeps/102
>>   [4]
>> https://github.com/marschall/jdk/ 
>> commit/207dac7e4d1bd65450bbd2c9e14d33fc34b7cebc
>>
>> Cheers
>> Philippe
>