Building for ARM systems

[Aleix Pol]

On Tue, Mar 14, 2017 at 11:54 AM, Dan Nicholson <nicholson at endlessm.com> wrote:
> On Mar 14, 2017 3:08 AM, "Alexander Larsson" <alexl at redhat.com> wrote:
>
> On Mon, 2017-03-13 at 22:31 -0500, Dan Nicholson wrote:
>> On Mar 13, 2017 9:19 PM, "Aleix Pol" <aleixpol at kde.org> wrote:
>>
>> $ flatpak build sdk bash
>> execvp bash: No such file or directory
>> $ cat /proc/sys/fs/binfmt_misc/status
>> enabled
>> $ ls -l /proc/sys/fs/binfmt_misc/qemu-arm
>> -rw-r--r-- 1 root root 0 mar 13 14:19 /proc/sys/fs/binfmt_misc/qemu-
>> arm
>>
>> Can you show the contents of that qemu-arm file?
>
> Yeah, it seems like it is dynamically linked and is not finding the
> loader.
>
>
> Nah, I just went through this debugging with someone at Endless yesterday.
> The kernel unfortunately returns ENOENT when it can't handle the binary
> format. Or possibly the ENOENT is because it can't find the interpreter for
> the binfmt. Either way, I'm pretty sure it's not a dynamic linking problem
> unless Aleix just installed the wrong package.
>
> What I suspect is actually the problem is that Debian's qemu-user-static
> package is setting a restrictive mask in the binfmt configuration that
> doesn't have the new F flag needed so that the interpreter is opened
> immediately at registration and kept open. I noticed yesterday that the
> setup on xenial is that the flags are set to OC. I'm guessing this hasn't
> been updated and can't really since it would make the configurations in the
> package dependent on a pretty new kernel. I believe the kernel throws EINVAL
> when an unrecognized option is in the mask.
>
> What Fedora does (I'm pretty sure), and what I think Debian should do, is
> leave the mask blank so the kernel defaults are used. Then you pick up the
> new F flag automatically when the kernel supports it.
>
> So, I'd like to see the actual registered configuration. If it contains OC
> like I suspect, then it needs to be updated to include F or just have the
> mask stripped off and use the kernel defaults.
>
> --
> Dan

It does include OC, not that I know what it means ^^'.

$ cat /proc/sys/fs/binfmt_misc/qemu-arm
enabled
interpreter /usr/bin/qemu-arm-static
flags: OC
offset 0
magic 7f454c4601010100000000000000000002002800
mask ffffffffffffff00fffffffffffffffffeffffff