RFR: 8309258: RISC-V: Add riscv_hwprobe syscall [v6]

[Robbin Ehn]

On Mon, 19 Jun 2023 08:04:32 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> Since ret is identical to 'p' (but larger), the number of chars is identical.
>> I don't have a system which return uarch in cpuinfo, and I have not seen one, so I can't test this path.
>> What are you testing on?
>> 
>> 
>> rehn at rv:~/source/gdb/binutils-gdb$ uname -a ; grep -i "uarch|mmu" /proc/cpuinfo  | uniq 
>> Linux rv 6.2.0-19-generic #19.1-Ubuntu SMP Fri Mar 31 12:41:53 UTC 2023 riscv64 riscv64 riscv64 GNU/Linux
>> mmu		: sv48
>> 
>> 
>> 
>> I don't mind pushing your suggested change, but I fail to understand how that can fix something :)
>
> Here is dump of file /proc/cpuinfo on hifive unmatched board:
> 
> $ cat /proc/cpuinfo
> processor       : 0
> hart            : 2
> isa             : rv64imafdc
> mmu             : sv39
> uarch           : sifive,u74-mc
> 
> processor       : 1
> hart            : 1
> isa             : rv64imafdc
> mmu             : sv39
> uarch           : sifive,u74-mc
> 
> processor       : 2
> hart            : 3
> isa             : rv64imafdc
> mmu             : sv39
> uarch           : sifive,u74-mc
> 
> processor       : 3
> hart            : 4
> isa             : rv64imafdc
> mmu             : sv39
> uarch           : sifive,u74-mc
> 
> 
> Since `ret = os::strdup(p + 2);`, I don't think `ret` and 'p' are identical. And here is what the old code does [1].
> 
> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/os_cpu/linux_riscv/vm_version_linux_riscv.cpp#LL128-L129

Fixed, pushed, thank for testing,

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PR Review Comment: https://git.openjdk.org/jdk/pull/14445#discussion_r1233703316