RE: How do I determine the ABI string used by pkg?

Mel Pilgrim <list_freebsd_at_bluerosetech.com> wrote on
Date: Thu, 02 Mar 2023 07:50:13 UTC :

> I need to determine the ABI string pkg uses on a given system, and need 
> to do so when there are no pkgs installed.

There may be more to that question than you are expecting
and you may have to establish more about what you want
(and why).

pkg itself is a package and so you have specified it is not
installed. You have not indicated why pkg can not be installed
the normal way and then used. (The question might be if this
can be unblocked or not.)

You have not indicated the range of system versions to be
covered. 12..14? All?

What about when an LP64 architecture is supported for also
running an ILP32 counterpart, so there are 2 ABIs?

LP64      ILP32 counterpart
amd64     i386
powerpc64 powerpc
mips64*   mips*
aarch64   armv6/armv7

(I question the accuracy of the armv6 in the "man 7 arch"
table, although I could change the kernel to switch from
armv7 to armv6 as the counterpart --and once helped someone
build a special kernel that did so.)

So how do you know which ABI you are interested in for
those?

> I've read through libpkg/pkg_elf.c and I can see how it's reading ELF 
> headers from well-known files. That's all easy enough to replicate, but 
> I'm a bit stuck on how it's determining the arch string for x86.

There are also examples like:

# pkg config ABI
FreeBSD:14:armv7

# pkg config ALTABI
freebsd:14:armv7:32:el:eabi:hardfp

Notably, "man 5 pkg.conf" does not even mention ALTABI , just
ABI .

Also, https://pkg.freebsd.org/ only lists the ABI form,
not the ALTABI form. But it does not mention riscv64 ,
riscv64sf , any mips64* , any mips* , sparc64 , 
plain "arm" , armeb , pc98 , ia64 , or alpha at all.

aarch64 is more like amd64:

# pkg config ABI
FreeBSD:14:aarch64

# pkg config ALTABI
freebsd:14:aarch64:64

But I'll note that I used the same machine (without
rebooting) for both armv7 and aarch64 above: armv7
was via a chroot and was without qemu involved (qemu
is not even installed).

Do you always have a already active execution context
to work with that is the one of interest, such as being
in a chroot?

> How/When does pkg decide to use FreeBSD:13:amd64 instead of 
> FreeBSD:13:x86:64?

It might be that it provides ALTABI but makes no use of it?
That would allow other things to make use of the extra
information in ALTABI text.

> Can I safely assume one or the other?

Likely purpose driven, no universal answer otherwise. You
may need to indicate what the ABI ( or ALTABI ) strings
are to be used for.

It used to be that some of the arm variants could be built
for either softfloat or hardfloat. Going back further some
that now have hardfloat instead used a form of softfloat.
It another example of your not having indicated the limits
on your range of interest in the possibilities over FreeBSD's
history.

===
Mark Millard
marklmi at yahoo.com