Support for allocation of executable memory

[Glavo]

Sorry, in the last sentence of that email, I wanted to say "just" instead
of "only".

I am using Google translate to write email. Please forgive me for my
problems in grammar and words.

Glavo <zjx001202 at gmail.com> 于2021年11月22日周一 上午3:00写道：

> which would involve maintaining a native dependency and building it for
>> every potential platform
>
>
> If it needs to be implemented through JNI, you may be right.
>
> However, for Panama, although we still need to use different codes for
> different operating systems, all this can be implemented through pure java
> code.
>
> Additional dependencies are unnecessary because these functions should be
> part of the operating system. Because it only needs to be implemented in
> Java code, it is not necessary to compile on multiple platforms.
>
>  not to mention the fact that every execution will have to pass through
>> JNI/Linker API
>
>
> I don't understand why you should emphasize this. Does this bring any
> additional problems?
>
>  I however disagree with the "just"
>
> This implementation does improve the difficulty of user code maintenance,
> but this function itself is low-level, unsafe and platform related, and the
> code using it is often platform related.
> So I believe that when it is really needed, the problems caused by this
> part are relatively insignificant, so I use the word "only".
>
> Felix Cravic <themode at outlook.fr> 于2021年11月22日周一 上午2:41写道：
>
>> I agree that there are reasons why it could not have its place in Panama,
>> like OS limitations complicating the API design & it being another pretty
>> unsafe feature.
>> I however disagree with the "just", which would involve maintaining a
>> native dependency and building it for every potential platform, not to
>> mention the fact that every execution will have to pass through JNI/Linker
>> API. By that point I doubt that Java would be the right tool for the job,
>> or is it perhaps what you meant?
>> ------------------------------
>> *De :* Glavo <zjx001202 at gmail.com>
>> *Envoyé :* dimanche 21 novembre 2021 19:19
>> *À :* Felix Cravic <themode at outlook.fr>
>> *Cc :* panama-dev at openjdk.java.net <panama-dev at openjdk.java.net>
>> *Objet :* Re: Support for allocation of executable memory
>>
>> I don't think Panama should provide special support for it.
>>
>> To do this, you just need to create the binding of the relevant system
>> API (e.g. `VirtualAlloc` and `VirtualProtect` on Windows, or `mmap` on
>> Linux) with the foreign linker API and call it.
>>
>> Felix Cravic <themode at outlook.fr> 于2021年11月22日周一 上午1:01写道：
>>
>> Hello, I was wondering if there has ever been any discussion about
>> supporting allocation of executable memory (and then its execution). The
>> use cases I have in mind are emulation, very hot paths requiring
>> specialized assembly (which could still fallback to jvm bytecode if
>> unavailable), and a potential option to keep the whole application written
>> in a JVM language.
>>
>> I doubt that such addition would drastically change the API, perhaps some
>> concern about OS specific restrictions (e.g. write-xor-execute memory
>> protection), and platform not supporting JIT compilation at all (IOS,
>> potentially problematic for Graal & project Leyden)
>>
>> Discussion would be appreciated!
>>
>>