Re: Cross compiling user applications for armv7

Ok, let's start from the beginning because I feel a little bit lost.
The buildenv concept is ok when you have no dependencies.
However, I have.

I see 3 potential options.
1. Use arm64 as an intermediate platform.
This is unacceptable approach for me.
2. Setup poudriere for armv7 manually.
I tried for 2 days and simply failed.
3. Setup qemu, and install dependencies and build custom code inside VM.

Solutions 2 and 3 are acceptable for me.
I guess 2 is better than 3, as it should be more performant.
However, I have no idea how to implement idea 2 or 3 in practice.
I also don't understand why setting up poudriere for armv7 is so hard.
What is missing by default that I can't do it with a single command?
Why the things that are missing are so hard to recreate manually?

Regards,
Michał Kruszewski

Sent with [Proton Mail](https://proton.me/mail/home) secure email.

On Saturday, September 13th, 2025 at 6:09 PM, Warner Losh <imp@bsdimp.com> wrote:

> On Sat, Sep 13, 2025 at 9:50 AM Michał Kruszewski <mkru@protonmail.com> wrote:
>
>> It is more about how hard it is to setup an environment for cross compiling your own kernel modules or applications for armv7.
>> I don't really care whether I use Buildroot way of doing things or FreeBSD way.
>> The difference is that with Buildroot it takes 10 minutes to setup such environment.
>> With FreeBSD I am struggling for two days.
>> And the only advice I get is to use arm64 machine.
>> Well, I don't have any.
>> And even if I had, I wouldn't use it, because I find this concept deeply "misengineered".
>
> And it is bad engineering. Mark sometimes gives bad advice that's based on his experience where it was "easier" to do it this way. I just wish I'd replied more quickly.
>
>> I know that you want to help, and I appreciate it.
>> I just feel frustrated with the complexity of this conceptually trivial task.
>
> No. I get it. I'm frustrated too since I've been working for years to make it better, and there's still these rough edges that turn people off.
>
> Warner
>
>> Regards,
>> Michał Kruszewski
>>
>> Sent with Proton Mail secure email.
>>
>> On Saturday, September 13th, 2025 at 4:29 PM, Mark Millard <marklmi@yahoo.com> wrote:
>>
>>>
>>> On Sep 13, 2025, at 00:20, Michał Kruszewski mkru@protonmail.com wrote:
>>>
>>> > Basically you are saying that I should have a separate physical arm64 machine for doing embedded armv7 development on FreeBSD.
>>> > If I understand this correctly, I just can't understand how can people say that FreeBSD is embedded friendly.
>>> > This is so much complex and convoluted compared to just using, for example, Buildroot on Linux.
>>> > This also doesn't feel like a *nix way of solving things.
>>> > I thought that after cross compiling world and kernel, there is some shell script that I can simply source to start cross-development for target platform.
>>>
>>>
>>> I found this AI based note about Buildroot's way of
>>> putting cross-build toolchains to use:
>>>
>>> QUOTE
>>> Buildroot pre-configures and compiles all necessarily
>>> packages during the build process to create a custom
>>> root filesystem.
>>> . . .
>>> Buildroot focuses on static builds, meaing all selected
>>> packages are compiled and integrated into the final root
>>> filesystem image during the build process. There is no
>>> concept of installing or updating packages on the target
>>> after the initial build.
>>> END QUOTE
>>>
>>> This is certainly not what the FreeBSD ports tree is
>>> set up for. Buildroot or analogous does not exist for
>>> FreeBSD --or most *BSD or Unix-- to my knowledge.
>>>
>>> May be NetBSD's pkgsrc cross build support:
>>>
>>> https://cdn.netbsd.org/pub/pkgsrc/current/pkgsrc/doc/HOWTO-use-crosscompile
>>>
>>> would be closer to how you like to work? (I've never
>>> used such.)
>>>
>>> > Regards,
>>> > Michał Kruszewski
>>> >
>>> > Sent with Proton Mail secure email.
>>> >
>>> > On Saturday, September 13th, 2025 at 12:23 AM, Mark Millard marklmi@yahoo.com wrote:
>>> >
>>> > > On Sep 12, 2025, at 14:10, Michał Kruszewski mkru@protonmail.com wrote:
>>> > >
>>> > > > A simple way is to set up an armv7 chroot / jail on an arm64 host such as a Raspberry Pi (Apple devices don't work!).
>>> > > > Then it's just like a native environment, but usually much faster.
>>> > >
>>> > > > I don't have physical arm64 host.
>>> > > > I also don't want to create a VM.
>>> > > > The whole idea seems weird and unnatural.
>>> > >
>>> > > Ignoring the RPi4B detail:
>>> > >
>>> > > FreeBSD official armv7 port-packages are built this way
>>> > > on arm64 hardware that natively supports user-space
>>> > > armv7 code. (ampere* systems are used.)
>>> > >
>>> > > FreeBSD official i386 port-packages are built this way
>>> > > on amd64 hardware that natively supports user-space
>>> > > i386 code.
>>> > >
>>> > > No use of qemu variants of any kind: no attempt at
>>> > > non-native-capable host environments.
>>> > >
>>> > > (Back when amd64 and qemu was used for the likes
>>> > > of armv7, lots of stuff failed to build mcuh of
>>> > > the time over the years --stuff that builds
>>> > > just fine now. This was abandoned after native
>>> > > became available. armv6 was always qemu based
>>> > > on amd64 and could not build much as of the last
>>> > > time a build was run.)
>>> > >
>>> > > > It sounds more like an exotic workaround.
>>> > >
>>> > > It is the official technique used for what FreeBSD
>>> > > distributes for armv7 port-packages.
>>> > >
>>> > > > Regards,
>>> > > > Michał Kruszewski
>>> > > >
>>> > > > Sent with Proton Mail secure email.
>>> > > >
>>> > > > On Friday, September 12th, 2025 at 10:46 PM, Robert Clausecker fuz@fuz.su wrote:
>>> > > >
>>> > > > > Hi Michał,
>>> > > > >
>>> > > > > A simple way is to set up an armv7 chroot / jail on an arm64 host such as
>>> > > > > a Raspberry Pi (Apple devices don't work!). Then it's just like a native
>>> > > > > environment, but usually much faster.
>>> > > > >
>>> > > > > Yours,
>>> > > > > Robert Clausecker
>>> > > > >
>>> > > > > Am Fri, Sep 12, 2025 at 04:19:42PM +0000 schrieb Michał Kruszewski:
>>> > > > >
>>> > > > > > Is there any tutorial on how to cross compile custom user application for armv7?
>>> > > > > > I struggle t find any.
>>> > > > > > Cross compiling the system is pretty easy.
>>> > > > > > However, how can one cross compile custom user application or kernel drivers.
>>> > > > > >
>>> > > > > > Regards,
>>> > > > > > Michał Kruszewski
>>> > > > > >
>>> > > > > > Sent with Proton Mail secure email.
>>> > > > >
>>> > > > > --
>>> > > > > () ascii ribbon campaign - for an encoding-agnostic world
>>> > > > > /\ - against html email - against proprietary attachments
>>> > >
>>> > > ===
>>> > > Mark Millard
>>> > > marklmi at yahoo.com
>>>
>>>
>>> ===
>>> Mark Millard
>>> marklmi at yahoo.com