Re: sys/modules/Makefile and MACHINE_ARCH vs arm64 (in use) vs aarch64 (not in use) VS. man arch; also COMPAT_FREEBSD32_ENABLED use

From: Mark Millard <marklmi_at_yahoo.com>
Date: Wed, 02 Aug 2023 19:56:42 UTC 
On Aug 2, 2023, at 11:16, Warner Losh <imp@bsdimp.com> wrote:

> Those all look wrong to me.
> 
> Warner 
> 
> On Wed, Aug 2, 2023, 11:27 AM Mark Millard <marklmi@yahoo.com> wrote:
> man arch reports:
> 
>            MACHINE       MACHINE_CPUARCH       MACHINE_ARCH
>            arm64         aarch64               aarch64
> . . .
>            arm           arm                   armv6, armv7
> 
> So I'd not expect arm64 in MACHINE_ARCH . But
> sys/modules/Makefile has (from a grep for MACHINE_ARCH):
> 
> .if ${MACHINE_ARCH} == "amd64" || ${MACHINE_ARCH} == "arm64"
> .if ${MACHINE_ARCH} == "amd64" || ${MACHINE_ARCH} == "arm64" || ${MACHINE_ARCH:Mpowerpc64*}
> 
> 
> Another issue may be that COMPAT_FREEBSD32_ENABLED is only
> put to use in the Makefile for MACHINE_CPUARCH being i386
> or amd64 :
> 
> .if ${MACHINE_CPUARCH} == "i386" || ${MACHINE_CPUARCH} == "amd64"
> _agp=           agp
> .if ${MACHINE_CPUARCH} == "i386" || !empty(COMPAT_FREEBSD32_ENABLED)
> . . .


I'll note that, for example, i386 vs. armv7 do not match
for some struct md_ioctl field offsets and the overall
size. Mike Karels is looking at getting struct md_ioctl32
correctly matching each of of the contexts: i386, (32-bit)
powerpc, and armv7.

I do not know if there are other COMPAT_FREEBSD32 adjustments
needed for differences in memory layout across the 3 (i386,
powerpc, armv7). md_ioctl I learned about via kyua test runs
and looking at the background for some things it reported for
armv7.

I've not found a clear indication of what is expected to work
for chroot/lib32 vs. what is not expected to work. It seems
one must look in the code and see if one finds conditional
material based, in part, on COMPAT_FREEBSD32. It might also
be that COMPAT_FREEBSD32 for i386 vs. armv7 vs. powerpc
might not be intending identical coverage for all I know.
So seeing COMPAT_FREEBSD32 might not be enough to know the
intent.


===
Mark Millard
marklmi at yahoo.com