On Monday, February 8, 2021, Florian Weimer fweimer@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 -- Red Hat GmbH, https://de.redhat.com/ , Registered seat: Grasbrunn, Commercial register: Amtsgericht Muenchen, HRB 153243, Managing Directors: Charles Cachera, Brian Klemm, Laurie Krebs, Michael
O'Neill
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