RFR: 8253795: Implementation of JEP 391: macOS/AArch64 Port [v9]

[Andrew Haley]

On Thu, 4 Feb 2021 09:49:17 GMT, Vladimir Kempik <vkempik at openjdk.org> wrote:

> > You read my mind, Andrew. Unless, of course, it's optimized to leverage the fact that it's thread-specific..
> 
> it's thread-specific
> 
> https://developer.apple.com/documentation/apple_silicon/porting_just-in-time_compilers_to_apple_silicon
> 
> > Because pthread_jit_write_protect_np changes only the current thread’s permissions, avoid accessing the same memory region from multiple threads. Giving multiple threads access to the same memory region opens up a potential attack vector, in which one thread has write access and another has executable access to the same region.

Umm, so how does patching work? We don't even know if other threads are executing the code we need to patch.

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PR: https://git.openjdk.java.net/jdk/pull/2200