RFR: 8309258: RISC-V: Add riscv_hwprobe syscall [v2]

[Robbin Ehn]

On Tue, 13 Jun 2023 14:05:51 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

>> Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   free uarch string
>
> src/hotspot/cpu/riscv/vm_version_riscv.hpp line 47:
> 
>> 45:     uint64_t    _feature_bit;
>> 46:     bool        _enabled;
>> 47:     int64_t     _value;
> 
> all but _enabled and _value could be const, ditto the accessor routines

Fixed

> src/hotspot/os_cpu/linux_riscv/vm_version_linux_riscv.cpp line 40:
> 
>> 38: 
>> 39: #ifndef HWCAP_ISA_I
>> 40: #define HWCAP_ISA_I  (1ULL << ('I' - 'A'))
> 
> nit: use the nth_bit() macro?

Sure fixed

> src/hotspot/os_cpu/linux_riscv/vm_version_linux_riscv.cpp line 99:
> 
>> 97:   char buf[1024] = {};
>> 98:   if (uarch != nullptr && strcmp(uarch, "") != 0) {
>> 99:     snprintf(buf, sizeof(buf), "%s,", uarch);
> 
> maybe assert for length < (sizeof(buf) - safety zone for the follow up strcat)

I did an alternative.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14445#discussion_r1229697121
PR Review Comment: https://git.openjdk.org/jdk/pull/14445#discussion_r1229697532
PR Review Comment: https://git.openjdk.org/jdk/pull/14445#discussion_r1229696890