[fedora-arm] Re: Questions for building RPMs for armel and armfp

[Peter Robinson]

On Sat, Jul 15, 2017 at 2:51 PM, fedora_arm

Hi Folks,
Apologies in advance if this is a FAQ. But I can't seem to find concrete
answers to what seem like relatively common questions.
The problem we have is the need to build current Fedora SRPMs for armel and possibly
armhf. We have an embedded product using an ARM926EJ-S core and another using a
Cortex-A9. Constraints dictate the RPMs to be built under in-house control and we're
trying to understand the path of least resistance and greatest reusability as Fedora
ARM moves forward.

Fedora hasn't supported anything less than ARMv7 (armhfp) since Fedora 18.

- So the first fundamental question is to what degree current Fedora SRPM content
supports cross platform builds on an x86_64 host? This would be our first
preference though it isn't clear to what extent the core project infrastructure
supports this, if at all.

No, we don't support cross compiling anything except the kernel.
There's lots of complexity in dealing with cross compiling and there's
code that's run during the builds that needs to run on the actual
architecture that's not actually compiling.

- Beyond cross builds infrastructure support is the question of what degree SRPMs
themselves support cross platform builds. This being an embedded platform, runtime
needs are minimal (no graphics, no heavy scripting languages, applications, etc..
So we're not faced with building a conventional workstation class RPM userland content.

I don't understand what you mean by that statement/question.

- My impression however is while some off-shoot efforts of Fedora ARM do build cross
platform, the main project release builds native on an ARM host. Moreover on bare metal
ARM vs. an ARM VM for efficiency. Is this correct? If so what are our options for
a build host Fedora ARM distribution at the present? Eg is a 32-bit ARM distro

The Fedora infrastructure runs 32 bit VMs as builders running on 64
bit hardware.

install required or will a 64-bit ARM install (eg: v8) be able to build SRPMs for
armel and armhf? The latter seems to be approaching a cross platform build, depending
upon what is available in a 64-bit Fedora ARM install now, and in the near future.

aarch64 is quite a bit different to ARMv7 in terms of instructions so
we don't support a multilib style env like x86_64/i686 does.
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[Neal Gompa]

On Sat, Jul 15, 2017 at 9:26 PM, fedora_arm

Post by Peter Robinson
Fedora hasn't supported anything less than ARMv7 (armhfp) since Fedora 18.

Not what I was hoping. But lack of an armel build isn't a long term issue.
Do any contemporary Fedora ARM derivatives exist which may still maintain
armel build infrastructure?

Yes. Pignus does: https://pignus.computer/

The current released image is Fedora 23 based, I believe. But their
Koji instance has been tracking current Fedora releases for some time:
http://koji.pignus.computer/koji/


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[Peter Robinson]

Post by Neal Gompa
On Sat, Jul 15, 2017 at 9:26 PM, fedora_arm

Post by Peter Robinson
Fedora hasn't supported anything less than ARMv7 (armhfp) since Fedora 18.

Not what I was hoping. But lack of an armel build isn't a long term issue.
Do any contemporary Fedora ARM derivatives exist which may still maintain
armel build infrastructure?

Yes. Pignus does: https://pignus.computer/
The current released image is Fedora 23 based, I believe. But their
http://koji.pignus.computer/koji/

Pignus is ARMv6 HFP, it's not armel and hence won't support ARM926EJ-S.
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[Peter Robinson]

On Sun, Jul 16, 2017 at 2:26 AM, fedora_arm

Post by Peter Robinson
Fedora hasn't supported anything less than ARMv7 (armhfp) since Fedora 18.

Not what I was hoping. But lack of an armel build isn't a long term issue.
Do any contemporary Fedora ARM derivatives exist which may still maintain
armel build infrastructure?

None I'm aware of, there's been a number of attempts for ARMv6 to
support original RPi/Pi Zero but even they're mostly dead.

Post by Peter Robinson
No, we don't support cross compiling anything except the kernel.
There's lots of complexity in dealing with cross compiling and there's
code that's run during the builds that needs to run on the actual
architecture that's not actually compiling.

My information admittedly is dated. When i was involved a number of years
ago, effort was being expended to support Fedora SRPM cross build by Marvell
and others IIRC. Appears moot now.

I've been involved in Fedora ARM for over 7 years, lead the build
effort since F-14 and we've never cross compiled except pre rpm phase
when boot strapping very core central bits of booting Linux for a new
arch IE armhfp or aarch64.

Post by Peter Robinson

- Beyond cross builds infrastructure support is the question of what degree SRPMs
themselves support cross platform builds. This being an embedded platform, runtime
needs are minimal (no graphics, no heavy scripting languages, applications, etc..
So we're not faced with building a conventional workstation class RPM userland content.

I don't understand what you mean by that statement/question.

I was assuming cross build of SRPMs may still be supported but probably wasn't
as complete as the case of a native build. That wouldn't likely have been an issue
for this embedded use case and the core userland runtime is most of what is
required. Again moot.

Well a SRPM is essentially noarch or agnostic so it doesn't matter
what arch you create it on it's consumable across all arches hence I
still don't understand what the question is.

Post by Peter Robinson
The Fedora infrastructure runs 32 bit VMs as builders running on 64
bit hardware.

64-bit ARM or x86_64 host hardware? If ARM is that leveraging kvm to accelerate
the 32-bit VM?

aarch64 as accelerated VMs using kvm. Not all aarch64 hardware supports that.

Post by Peter Robinson
aarch64 is quite a bit different to ARMv7 in terms of instructions so
we don't support a multilib style env like x86_64/i686 does.

So the model is a strict self-hosted native build where the host's distro and
toolchain is exactly that of the target, correct?

Correct.
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[Neal Gompa]

On Sun, Jul 16, 2017 at 12:40 PM, fedora_arm

Post by Peter Robinson
On Sun, Jul 16, 2017 at 2:26 AM, fedora_arm

Post by Peter Robinson
Fedora hasn't supported anything less than ARMv7 (armhfp) since Fedora 18.

Not what I was hoping. But lack of an armel build isn't a long term issue.
Do any contemporary Fedora ARM derivatives exist which may still maintain
armel build infrastructure?

None I'm aware of, there's been a number of attempts for ARMv6 to
support original RPi/Pi Zero but even they're mostly dead.

Well this isn't exactly surprising for a server/workstation class
distribution to drop active support & soak for what has become
an obsolete/obsoleting embedded architecture.
The sole reason in pursuing the possibility is Fedora distro SRPM
content being a strong preference as a distro intake choice for
this customer. The armel product is essentially in maintenance
mode and worst case would be to create a one-off build solution.
The practicality of that approach is what I'm trying to understand.

The only armel/armsfp RPM-based distribution I know of is Mageia
(since Pignus is apparently not one). Their Mageia 6 release has an
armv5tl flavor in addition to the standard armv7hl flavor.

I think that armsfp is basically dead in most distributions, in part
due to the abundance of armhfp hardware replacing the old armsfp
stuff.


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