Re: Phone call (was Re: Armhf dynamic linker path)

[Michael Hope <michael dot hope at linaro dot org>]

2012/4/12 Paulo César Pereira de Andrade
<paulo.cesar.pereira.de.andrade@gmail.com>:
> Em 11 de abril de 2012 21:16, Michael Hope <michael.hope@linaro.org> escreveu:
>> 2012/4/12 Paulo César Pereira de Andrade
>> <paulo.cesar.pereira.de.andrade@gmail.com>:
>>> Em 11 de abril de 2012 20:22, Michael Hope <michael.hope@linaro.org> escreveu:
>>>> On 12 April 2012 10:38, Steve McIntyre <steve.mcintyre@linaro.org> wrote:
>>>>> On Wed, Apr 11, 2012 at 02:06:09AM +0100, Steve McIntyre wrote:
>>>>>>
>>>>>>And here's the details as promised.
>>>>>>
>>>>>>I've started a wiki page at
>>>>>>
>>>>>>https://wiki.linaro.org/OfficeofCTO/HardFloat/LinkerPathCallApr2012
>>>>>>
>>>>>>with a strawman agenda for now, and a Doodle poll at
>>>>>>
>>>>>>http://www.doodle.com/93bitkqeb7auyxn7
>>>>>>
>>>>>>to see when the best time is for the call on Thursday/Friday. Please
>>>>>>fill in the times that work for you ASAP and I'll announce the result
>>>>>>during Wednesday. Ideally we'd like stakeholders from all the relevant
>>>>>>distros and the upstream toolchain developers to be there, able to
>>>>>>represent their groups and (importantly) able to make a decision here
>>>>>>on what we should do.
>>>>>>
>>>>>>Apologies for the short notice, but we need a decision quickly.
>>>>>
>>>>> And the best time turns out to be Friday at 15:00 UTC (16:00 BST,
>>>>> 11:00 EDT etc.). Of the 10 people who responded in the poll, the only
>>>>> person who can't make that time is Michael in .nz. Sorry, Michael.
>>>>
>>>> All good. ?My vote is for /lib/ld-arm-linux-gnueabihf.so.3 as it:
>>>> ?* is similar to /lib/ld-x86-64.so.2
>>>> ?* keeps the libraries and loader in the same directory
>>>> ?* doesn't invent a new /libhf directory
>>>> ?* is easier to implement in GLIBC
>>>> ?* is architecture and ABI unique
>>>> ?* requires less change for distros where the hard float libraries are
>>>> already in /lib
>>>
>>> ?Sorry for more bikeshedding, but afaik rpm based distros are
>>> using the armv7hl identifier, so it could as well be
>>>
>>> /lib/ld-linux-armv7hl.so.3
>>
>> This includes the ABI (h), adds the endianess (l), and implies a
>> architecture level (v7). ?The name for the most common configurations
>> should be as short as possible so I'd rather drop the 'l' and add a
>> 'b' or 'eb' if anyone wants a big endian distro in the future. ?The
>> architecture level is a problem as the loader should also be valid on
>> ARMv5 and ARMv6 hard float builds. ?Skype should be able to make a
>> hard float binary that runs on everything, including a potential ARMv6
>> hard float RaspberryPi build.
>
> ?This means ld.so (and what else? a skype binary should not come fully
> statically linked) should be built with -march=armv5te? That is, common
> denominator should be vfpv3-d16, ldrd/strd and thumb2 instruction set?
> ?AFAIK, for "user level", armv6 with vfp is effectively amv7 (sans armv7-r
> that has a div instruction in thumb mode).

The architecture and feature set is a different topic and should be
discussed by the distros but I'd rather finish the loader path one
first.  Note that Fedora, Ubuntu, Debian, openSUSE, and Gentoo have
all taken the opportunity to go to ARMv7 at the same time as switching
to hard float.

-- Michael