RFR: 8345296: AArch64: VM crashes with SIGILL when prctl is disallowed [v3]

[Aleksey Shipilev]

On Mon, 2 Dec 2024 16:18:14 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>>> But I don't quite get what are you suggesting?
>> 
>> As the doc mentions a negative result, my suggestion to add an assert can be ignored.
>
>> As the doc mentions a negative result, my suggestion to add an assert can be ignored.
> 
> Where do you see this assert going?
> 
> 
>   if (UseSVE > 0) {
>     int vl = get_current_sve_vector_length();
>     if (vl < 0) {
>       warning("Unable to get SVE vector length on this system. Disabling SVE. Specify -XX:UseSVE=0 to shun this warning.");
>       FLAG_SET_DEFAULT(UseSVE, 0);
>     } else {
>       _initial_sve_vector_length = vl;
>     }
>   }
> 
> 
> We are already checking `< 0` path here. Checking for `> 0` formally does not follow the docs, because the call can formally return `0` without claiming this is an error. What we should be doing is testing the value `get_current_sve_vector_length()` giving us -- that I think is done in current PR.

New commit adds more comprehensive checks.

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PR Review Comment: https://git.openjdk.org/jdk/pull/22479#discussion_r1866204286