RFR: 8295264: Fix PaX check on RISC-V

[Fei Yang]

On Mon, 17 Oct 2022 08:55:23 GMT, Fei Yang <fyang at openjdk.org> wrote:

>>> I see the LKML link mentions this: "Just remove the check altogether and let PROT_WRITE imply PROT_READ as is the case on other architectures.". Is this change still necessary then? Thanks.
>> 
>> That would be necessary for any older version of Linux. Also, it allows it to match all other calls to `::mmap` in hotspot.
>
>> > I see the LKML link mentions this: "Just remove the check altogether and let PROT_WRITE imply PROT_READ as is the case on other architectures.". Is this change still necessary then? Thanks.
>> 
>> That would be necessary for any older version of Linux. Also, it allows it to match all other calls to `::mmap` in hotspot.
> 
> That makes sence to me. Changes looks good to me.

> Hi @RealFYang @luhenry, do you think it is necessary to back-port this commit to jdk19u branch? Thanks!

@XieJiSS : Are you using jdk19u and affected by this issue? AFAIK, this is also handled on the kernel's side.

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PR: https://git.openjdk.org/jdk/pull/10690