+++ Jon Masters [2012-09-16 21:34 -0400]:
> On 09/13/2012 01:24 PM, Mike Frysinger wrote:
> > On Thu, Sep 13, 2012 at 9:33 AM, Steve McIntyre wrote:
> >> On Mon, Sep 10, 2012 at 03:39:20PM -0400, Mike Frysinger wrote:
> >>> On Mon, Sep 10, 2012 at 2:56 PM, Jon Masters wrote:
> >>>> I propose the following triplet for Fedora on AArch64:
> >>>>
> >>>> aarch64-redhat-linux-gnu
> >>>>
> >>>> Skipping the vendor part, that means generally:
> >>>>
> >>>> aarch64-linux-gnu
> >>>>
> >>>> There should be no reason to deviate from this. I'm putting it out there 
> >>>> now
> >>>> because I don't want another ARMv7 experience later :)
> >>>
> >>> unless you're doing big endian then it's:
> >>>  aarch64_be-linux-gnu
> >>
> >> In discussions with various folks, it seems that none of the distros
> >> are particularly interested in BE. \o/
> > 
> > i was just more nettling Jon ;)
> 
> Always fun. Note that just because we agree on the triplet, doesn't mean
> that we've yet had the fun of discussing the linker path until we pass
> out form sheer exhaustion. So, let's have that one out before some of us
> go doing our own thing. From my point of view, we don't care /at all/
> about multi-arch and certainly I have no plans of even supporting a
> 32-bit ARM userspace on AArch64 (if you want that, use virtualization).
> Sure, the latter is aspirational and someone will ruin it, so maybe we
> need to go to /lib64 rather than /lib (I don't want to). 

Or do it properly with multiarch: :-)
/lib/aarch64-linux-gnu
/lib/arm-linux-gnueabihf

> But just
> because I don't like multi-arch doesn't mean we shouldn't know if
> Debian/Ubuntu are going to do a different linker path again? :)
 
> In other words, I can live with whatever, but let's do it one way the
> first time, rather than repeating what happened with ARMv7. So, what are
> Debian and Ubuntu going to do for multi-archification of AArch64?

Multi-arch support and libc linker/loader path are mostly independent.
All that is needed is that the linker path for each ABI is unique (and
agreed).

The original aarch64 work was all done using a multi-arch style linker path,
just for consistency: 
/lib/aarch64-linux-gnu/ld.so.1

But as that has proved unpopular with upstream, the patches which I
believe are imminent upstream have used 
/lib/ld-linux-aarch64.so.1 
and 
/lib/ld-linux-aarch64_be.so.1 
to be consistent with what was thrashed out recently as acceptable to
everbody on this list and in telcons.

Debian and Ubuntu (and other derivatives) will use "aarch64-linux-gnu"
(ie the same as the gnu triplet) for the multiarch tuple, so libraries
will be in /lib/aarch64-linux-gnu and /usr/lib/aarch64-linux-gnu

The upstream patches have used the existing (poor man's
multiarch) paths:
/lib64
/usr/lib64
in order to make them fit in with existing upstream convention.

Now, I'm in agreement with Jon, and would much prefer to see them in
/lib, but I was outvoted :-)

The focus currently is on upstreaming architecture support _without_
having to also have a big fight about the benefits or otherwise of
multiarch.

Personally I think that's a mistake and we'll just be stuck with the
limited 'lib64' hack for another 10 years, at least outside
Debian-world, but ultimately if that's what most libc/toolchain
maintainers still want then we can all live with that (at the expense
of significant divergence between library paths used in distros, but
that's been true for a decade already and we all survived).

If we could agree on world where you could build for _either_ a
single-ABI world (everything in /lib), _or_ a multiarch world
(everything in /lib/<tuple>) that would make a lot of sense to me. The
current options of '64/32 only multilib-style multiarch' or 'proper
multiarch' seems suboptimal.

So the short answer is that currently the aarch64 patches are totally
un-multiarch, and fit in with current agreed upstream practice. So if
you think multiarch is nonsense, and multilib is just fine, say
nothing and all will be hunky-dory :-)

If you prefer /lib over /lib64 or /lib/<ABI-tuple> over /lib64 then
now would be a good time to speak up. 

This bikeshed isn't finished yet.

Wookey
-- 
Principal hats:  Linaro, Emdebian, Wookware, Balloonboard, ARM
http://wookware.org/

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