Building for ARM systems

[Aleix Pol]

On Sat, Mar 18, 2017 at 1:00 AM, Aleix Pol <aleixpol at kde.org> wrote:
> On Fri, Mar 17, 2017 at 6:28 PM, Dan Nicholson <nicholson at endlessm.com> wrote:
>> On Thu, Mar 16, 2017 at 8:56 PM, Aleix Pol <aleixpol at kde.org> wrote:
>>>
>>> I've been trying it for a bit more, I am getting these contents now,
>>> still getting the same execvp error message.
>>>
>>> # cat /proc/sys/fs/binfmt_misc/qemu-arm
>>> enabled
>>> interpreter /usr/bin/qemu-arm-static
>>> flags:
>>> offset 0
>>> magic 7f454c4601010100000000000000000002002800
>>> mask ffffffffffffff00fffffffffffffffffeffffff
>>
>> Ah, I lied. I thought that the behavior of the kernel was to make the
>> new "F" feature default if the flags were not set. Now I actually
>> tried on yakkety and it fails. Here's my full working test recipe.
>>
>> # apt-get install qemu-user-static
>> # update-binfmts --package qemu-user-static --remove qemu-arm
>> /usr/bin/qemu-arm-static
>> # echo ":qemu-arm:M::\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff:/usr/bin/qemu-arm-static:OFC"
>>> /etc/binfmt.d/qemu-arm.conf
>> # systemctl restart systemd-binfmt.service
>> # cat /proc/sys/fs/binfmt_misc/qemu-arm
>> enabled
>> interpreter /usr/bin/qemu-arm-static
>> flags: OCF
>> offset 0
>> magic 7f454c4601010100000000000000000002002800
>> mask ffffffffffffff00fffffffffffffffffeffffff
>>
>> The OC aren't to my knowledge needed, but that just maintains the way
>> that the qemu-user-static set it up with the additional F flag. Now
>> for a test with a debootstraped armhf system. Note that if the above
>> isn't working, I'd have to use qemu-debootstrap which copies
>> /usr/bin/qemu-arm-static into the target system.
>>
>> # apt-get install debootstrap debian-archive-keyring
>> # debootstrap --arch=armhf unstable unstable
>> # chroot unstable ls
>> bin   dev  home  media    opt   root  sbin  sys  usr
>> boot  etc  lib     mnt    proc  run   srv   tmp  var
>>
>> Success! I haven't actually tested flatpak yet in this scenario, but
>> I'm confident it will succeed.
>>
>> Looks like there's a debian bug for supporting the F flag in
>> binfmt-support -
>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=853820. After that
>> the qemu-user-static package would need to be updated to make use of
>> the new binfmt-support feature. Or, even better, binfmt-support adds F
>> by default if the kernel supports it with maybe an option to disable
>> it.
>
> Oh, I see. Well, this makes me happy, now it's compiling things!
> Terribly slow, but it is doing things. I'll leave it overnight and see
> how far we can go.
>
> Thank you a lot, Dan!
> Aleix

Hi,
Just to remind what's the status, I left it building, it mostly
worked. It got stuck when linking QtWebEngine, I guess my system (16
GiB of RAM) couldn't take the the hit on qemu:

/usr/lib/gcc/arm-unknown-linux-gnueabi/5.2.0/../../../../arm-unknown-linux-gnueabi/bin/ld.gold:
fatal error: libQt5WebEngineCore.so.5.7.1: mmap: failed to allocate
2215618340 bytes for output file: Cannot allocate memory

Thank you again!

Regards,
Aleix