[Arm-dev] Chrooting/Docker to armv7hl and armv5tel on aarch64

[Gordan Bobic]

I did a bit more digging, and rebuilding 4.9.153 with CONFIG_COMPAT and a
few related options, had an effect - no longer do I get "exec format error"
- now it just outright segfaults.
4.4.172 works perfectly.

I'm using clean mainline kernels with no additional patches.

chrooting to aarch64 chroots works.


On Sat, Jan 26, 2019 at 6:07 PM Stephen John Smoogen <smooge at gmail.com>
wrote:

>
>
> On Sat, 26 Jan 2019 at 18:45, Gordan Bobic <gordan at redsleeve.org> wrote:
>
>> Yes, they are "wrong", but not "WRONG!".
>>
>> As I (possibly poorly) explained, I'm running on an aarch64 machine, but
>> am trying to run armv5tel and armv7hl chroots.
>> I just dug out an old kernel I was using (4.4.72) and I can now chroot
>> just fine.
>>
>> So it's something that changed in the kernel, but I'm not sure what else
>> it could be other than the page size (which I already checked).
>>
>> I'm going to build the latest 4.4.172 with my 4.4.72 config and see if
>> that works. If it does, I'll try to make oldconfig that on 4.9.153 and try
>> again, see if that breaks things again. I was just hoping there might be an
>> option I missed in 4.9 that enables/disables downward compatibility.
>>
>>
> The places I have seen where  this breaks before was
> * it works on only specific  aarch64 devices
> * it works but only after you update the firmware to a newer vendor
> version (because the kernel expects that to fix something else)
> * it is a regression and needs to be fixed.
>
> [The first one was where someone remembered it working but forgot they
> were  working on XYZ box and then replicated in ABC and found the arch
> didn't have that.]
>
> I am expecting it is going to be 3... but I would check on 2 also.
>
>
>
>> Gordan
>>
>> On Sat, Jan 26, 2019 at 5:41 PM Stephan GUILLOUX <
>> stephan.guilloux at free.fr> wrote:
>>
>>> Wrong architecture binaries, in the chroot'ed folder ?
>>>
>>> What do you get with:
>>>
>>>      file <chroot>/bin/bash
>>>
>>> On 26-Jan-19 17:49, Gordan Bobic wrote:
>>> > It's been so long since I last had to do this, that it looks like a
>>> > kernel update somewhere along the way broke this for me. :-(
>>> >
>>> > What happens now:
>>> >
>>> > # chroot rs7
>>> > chroot: failed to run command ‘/bin/bash’: Exec format error
>>> >
>>> > I could have sworn that this was all I needed to make this work last
>>> time:
>>> > # grep 4K_PAGES config-4.9.153-1.el7.centos.aarch64
>>> > CONFIG_ARM64_4K_PAGES=y
>>> > # CONFIG_ARM64_64K_PAGES is not set
>>> >
>>> > Unfortunately, now trying to chroot into either hard-float or
>>> > soft-float chroot results in the exec format error.
>>> >
>>> > Looking at time stamps of various things, I had this working with
>>> > 4.4.70, but have since switched to 4.9.x kernels. Any thoughts on what
>>> > changed between 4.4 and 4.9 would be most appreciated.
>>> >
>>> > What am I missing?
>>> >
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>
>
> --
> Stephen J Smoogen.
>
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