RFR: JDK-8147388: Add diagnostic commands to attach JVMTI agent.

[Staffan Larsen]

This is a good improvement overall.

The new diagnostic commands need to have proper permissions set: 

   static const JavaPermission permission() {
      JavaPermission p = {"java.lang.management.ManagementPermission",
                         “control", NULL};
     return p;
  }

And as David said: tests! See hotspot/test/serviceability/dcmd/jvmti.

Thanks,
/Staffan

> On 14 jan. 2016, at 15:00, Yasumasa Suenaga <yasuenag at gmail.com> wrote:
> 
> Hi all,
> 
> We can use Attach API to attach JVMTI agent to live process.
> However, we have to write Java code for it.
> 
> If we can attach JVMTI agents through jcmd, it is very useful.
> So I want to add two new diagnostic commands:
> 
> * JVMTI.agent_load: Load JVMTI native agent.
> * JVMTI.javaagent_load: Load JVMTI java agent.
> 
> I maintain two JVMTI agents - HeapStats [1] and JLivePatcher [2].
> [1] is native agent, [2] is java agent.
> They provide a program for attaching to live process.
> 
> I guess that various JVMTI agents provide own attach mechanism like them.
> I think that we should provide general way to attach.
> 
> I've uploaded webrev. Could you review it?
>  http://cr.openjdk.java.net/~ysuenaga/JDK-8147388/webrev.00/
> 
> I'm jdk9 committer, however I cannot access JPRT.
> So I need a sponsor.
> 
> 
> Thanks,
> 
> Yasumasa
> 
> 
> [1] http://icedtea.classpath.org/wiki/HeapStats
> [2] https://github.com/YaSuenag/jlivepatcher  (in Japanese)