On Monday, February 8, 2021, Florian Weimer <fweimer(a)redhat.com> wrote:
* Robert Scheck:
> Trying to follow the path on how to get Fedora for ppc64le to a
"POWER-Pi",
> I had to learn that glibc developers seem to treat IBM POWER9
strictly
equal
> to ABI rules rather handling the different features more fine
granulated. My
> understanding here might be imprecise or wrong, this is what I
understood
> and I'm no expert at this topic. Nevertheless I'm trying to precise it a
bit
> more:
> The IBM Power ISA Version 3.1 [10] specifies on page 8
compliancy
subsets,
> where the Linux Compliancy Subset (LCS) is explained on page 10
ff. Page
11
> refers specifically to the "Scalar Float Optional
Features" and mentions
in
> the first row of the table VSX. However what seems to be
implemented e.g.
> in glibc is something like "#ifdef POWER9" rather "#ifdef
HARDWAREFEATURE",
> which effectively makes VSX support mandatory rather optional.
The OpenPOWER 64-Bit ELF V2 ABI Specification makes VSX support
non-optional, as far as I can tell. If it does not, that would be a bug
in the document because it's definitely the intent.
'scuse my language, i have to say it... arse.
i checked the ELF v2 PDF, it specifically mentions VSX.
It is possible to define a different ABI without VSX support, but it
would have a different GNU triplet (not powerpc64le-*-linux-gnu) and a
different RPM architecture (not ppc64le).
i found this:
https://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html
which appears to be a supplemental of the old PowerPC 64 bit ELF V1 ABI.
no mention of VSX is made in that document.
do you (or anyone) happen to know the history here?
The first step would be to work with the OpenPOWER Foundation to
define
that new ABI.
if ELFV1 64 bit was preexisting that may not be necessary to define (which
would be a huge relief)
Then port the GNU and LLVM toolchains to it.
joy :)
Afterwards,
a new Fedora architecture can be brought up if the Fedora project
supports adding the architecture.
and every other distro on the planet.
deep breath.
ok. thank you Florian for the insights.
l.
Thanks,
Florian
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