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Date:      Thu, 12 Feb 2015 12:15:16 -0500
From:      Ed Maste <emaste@freebsd.org>
To:        Warner Losh <imp@bsdimp.com>
Cc:        "freebsd-arm@freebsd.org" <freebsd-arm@freebsd.org>
Subject:   Re: FreeBSD/arm64 MACHINE/MACHINE_ARCH identification
Message-ID:  <CAPyFy2BKzhiA4tbi-mXd6T114_zawmWTi3XbyXiUcgijQfHdyw@mail.gmail.com>
In-Reply-To: <228428CC-4042-4902-90A4-E7040F4BFFF5@bsdimp.com>
References:  <CAPyFy2A=Ev5gdYPKgEE0LS3-1sY%2BXmkZA7VCe71E6Fmbb=vMRw@mail.gmail.com> <607BF592-A09B-4DB4-9872-C9E63066AB57@bsdimp.com> <CAPyFy2Bgrap3TkFNuChyMC0Vwbjdt5FVW0ey03XtkK1iwNL1KQ@mail.gmail.com> <71E9C1B9-F819-420B-90A5-A36D58E71817@bsdimp.com> <CAPyFy2ATn5xgsvePCdvzqnyBS45izVHdL8yLaQQoKeJenSv9tg@mail.gmail.com> <228428CC-4042-4902-90A4-E7040F4BFFF5@bsdimp.com>

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>> Oh - I don't care what directory Linux puts the kernel source in, only
>> what's reported by uname.  As far as I can tell that has always been
>> aarch64 for uname -m.
>
> Traditionally in Linux, they have been a matched set.

Ok, it appears they may have abandoned this.

>> We might decide that "uname -m" has to be aarch64 to match
>> expectations of third-party software set by other operating systems.
>> If that in turn means we have to move the kernel source, so be it.
>
> This one I=E2=80=99m not on board with. You=E2=80=99ve not made a compell=
ing case for
> it yet.

That's why I said "we might decide" -- I'm not sure myself.

However, there's no backwards compatibility concern here, we've never
had a FreeBSD release that reports "arm64" for "uname -m". There's no
reason for us to prefer "arm64" if everyone else uses "aarch64."
Also, having arm64 for uname -m and aarch64 for uname -p seems a bit
odd.

> One other area that these choices impact the system is in the MACHINE_CPU=
ARCH
> macro, which is derived from MACHINE_ARCH (-p), so it might need another
> special case.

There's a special case already for TARGET_TRIPLE :C/arm64/aarch64/.

> There=E2=80=99s also a number of places we test different of these variab=
les
> against arm*<mumble> that will need to be audited if we make this change =
as well.
> Thankfully, there=E2=80=99s only about a dozen. While not externally visi=
ble, any change here
> will need to make sure we=E2=80=99re consistent when building.

Yes, I'm not too worried about the naming within our tree - dealing
with a few dozen tests in the FreeBSD tree is much easier than trying
to change expectations of third-party software.



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