Re: Detection of hadware feature => please do not use signal

Thomas Munro <thomas(dot)munro(at)gmail(dot)com> writes:
> Unfortunately it looks like NetBSD doesn't put AT_HWCAP into its
> auxv[], or even expose it to user space nicely, and those libraries
> don't seem to know of another way. Hopefully NetBSD will align with
> those other systems for portability's sake. The only other way I
> could find in a quick googling session is /usr/sbin/cpuctl, root only,
> no cigar (but a solid clue that the information is floating around
> somewhere, it just depends where exactly the root-only fencing is
> happening).

I poked into this with NetBSD and found that cpuctl's "identify"
option works just fine without root. So that motivated me to dig
into its source code, and I end up with the attached. Sadly it only
works in 64-bit; there is presumably a way to detect this in 32-bit
as well, but cpuctl doesn't know it. That doesn't bother me a whole
lot though, at least not nearly as much as the 64-bit case. Anybody
running PG on 32-bit ARM shouldn't be expecting great performance.

I've checked this on NetBSD 9.2 and 10.0. I don't have hardware
that should return false (and there may not be any such 64-bit
hardware anyway...), so there's not much more I can test.

regards, tom lane