uname -m/-p for compat32 binaries

[John Baldwin]

On Tuesday, July 20, 2010 1:51:27 pm Garrett Cooper wrote:
> On Tue, Jul 20, 2010 at 6:07 AM, John Baldwin <jhb at freebsd.org> wrote:
> > On Monday, July 19, 2010 5:30:54 pm Kostik Belousov wrote:
> >> Hi,
> >> I intend to commit the following change, that makes sysctls
> >> hw.machine_arch and hw.machine to return "i386" for 32 bit
> >> binaries run on amd64. In particular, 32 bit uname -m and uname -p
> >> print "i386", that is good for i386 jails on amd64 kernels.
> >>
> >> I find the change very useful for me, but I wonder why such trivial
> >> modification is not yet done. Can anybody note a possible fallout from
> >> it ?
> >
> > Presumably ia64 and powerpc64 would need a similar change as well?  It looks
> > fine to me.  I suspect Y! used the UNAME_* approach as it didn't add yet-
> > another local diff to maintain in the kernel, and the uname fixes at Y! might
> > have predated SCTL_MASK32.
> 
> I thought amd64 was a special case because we run biarch, whereas ia64
> was always 64-bit...
> 
> Wouldn't this change also create problems later on down the line when
> we're no longer biarch?

amd64 is not biarch, it just supports FreeBSD/i386 binaries similar to how
FreeBSD/i386 supports Linux/i386 binaries.  Kostik's patch makes a
FreeBSD/i386 uname binary report that it is running under FreeBSD/i386 just
as we currently make a Linux/i386 uname binary report that it is running
under Linux/i386.

ia64 and powerpc64 both support COMPAT_FREEBSD32 similar to amd64.
COMPAT_FREEBSD32 for amd64 and ia64 supports FreeBSD/i386 binaries.
COMPAT_FREEBSD32 for powerpc64 supports FreeBSD/powerpc binaries.

-- 
John Baldwin