RFR: 8345296: AArch64: VM crashes with SIGILL when prctl is disallowed [v2]

[Aleksey Shipilev]

On Mon, 2 Dec 2024 13:14:24 GMT, Evgeny Astigeevich <eastigeevich at openjdk.org> wrote:

>> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Review comments
>
> src/hotspot/cpu/aarch64/vm_version_aarch64.cpp line 447:
> 
>> 445: 
>> 446:   if (UseSVE > 0) {
>> 447:     _initial_sve_vector_length = get_current_sve_vector_length();
> 
> We need an assert checking `_initial_sve_vector_length > 0`

Speaking of the valid ranges for SVE vector length, I don't think we want to blindly accept any `>0` value either. There is a block downwards that tries to check that vector length is not smaller than a `FloatRegister::sve_vl_min`, and that it is a power of two. But that block only works for manual overrides of `MaxVectorSize`. I say we co-opt that block for checking the `prctl` result on a common path. See new commit?

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PR Review Comment: https://git.openjdk.org/jdk/pull/22479#discussion_r1866026850