On Sun, 11 May 2025 04:57:44 GMT, Ioi Lam <ik...@openjdk.org> wrote:
> https://openjdk.org/jeps/483 mentions:
>
>> To enjoy the benefits of the AOT cache generated during a training run, the
>> training run and all subsequent runs must be essentially similar. [...] All
>> runs must not use JVMTI agents that can arbitrarily rewrite classfiles
>> using ClassFileLoadHook.
>
> However, when *any* java agent is specified in the training run, the JVM
> fails at start-up. E.g.,
>
>
> $ java -XX:AOTMode=record -javaagent:agent.jar -cp app.jar App
> Error occurred during CDS dumping
> Must enable AllowArchivingWithJavaAgent in order to run Java agent during CDS
> dumping
>
>
> With the AOT cache, the main concern for JVMTI agents is that they can modify
> the contents of loaded Java classes. If we store such modified classes into
> the AOT cache, their contents will no longer match the original class files
> (from application JAR files, etc). As a result, when using the AOT cache in
> production runs, the application may have unexpected behavior.
>
> With this PR, we allow JVMTI agents in the AOT workflow. To address the above
> concern, we ensure that JVMTI agents cannot affect the contents of AOT cache:
>
> - In training runs (`java -XX:AOTMode=record`), JVMTI agents are allowed,
> but the AOT configuration file should filter out classes that are transformed
> by the agents. This can be checking `InstanceKlass::has_been_redefined()` and
> `ClassFileStream::from_class_file_load_hook()`.
>
> - In the assembly phase (`java -XX:AOTMode=record`), agents can be specified
> in the command-line. However, since the assembly phase doesn't execute any
> application logic, we will also not load any of the specified agents.
> Therefore, the agents cannot affect the contents of the AOT cache created in
> the assembly phase.
src/hotspot/share/prims/jvmtiAgentList.cpp line 79:
> 77: JvmtiAgent* next = head(list);
> 78: #if INCLUDE_CDS
> 79: if (_disable_agent_list) {
Instead of intercepting here would it be better if we can clear
`JvmtiAgentList::_list` in `CDSConfig::check_aotmode_create()`?
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/25170#discussion_r2087603909
