RFR: 8310656: RISC-V: __builtin___clear_cache can fail silently. [v2]

[Robbin Ehn]

On Fri, 30 Jun 2023 08:56:02 GMT, Robbin Ehn <rehn at openjdk.org> wrote:

>> Hi, please consider.
>> 
>> We recently had a bug where user were missing permissions to use this syscall.
>> Which caused crashing on, according to hs_err on things like "addi x11, x24, 0" with SIGILL.
>> If it fails it is even possible to execute valid but 'old' instruction which may not lead to a crash, instead the program misbehaves.
>> 
>> To avoid this mess I suggest that we first test the syscall during vm init and we use it directly.
>> This way we can make sure it never fails.
>> 
>> Tested failing syscall with qemu, tested t1 in qemu, t1 on jh7110 in-progress.
>
> Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   added back data barrier
>   
>   Signed-off-by: Robbin Ehn <rehn at rivosinc.com>

Merge and updated for:
"[8311145](https://bugs.openjdk.org/browse/JDK-8311145) Remove check_with_errno duplicates".
and those nits.

Thanks @RealFYang @tstuefe !

@RealFYang Let me know if that flush address update is better!

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PR Comment: https://git.openjdk.org/jdk/pull/14670#issuecomment-1615851309