Date: Mon, 17 Feb 2020 11:12:00 +0200
From: Timo Teras <timo.teras@iki.fi>
To: Carl Chave <online@chave.us>
Cc: ~alpine/apk-tools@lists.alpinelinux.org
Subject: Re: APK Package Name Issue on armel port
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Hi,

On Mon, 17 Feb 2020 00:59:10 -0500
Carl Chave <online@chave.us> wrote:

> The odd results of a few more tests and then I'll stop spamming the
> list for help on an unsupported architecture:
>[snip]

Those sound really weird. 

> uname -a for comparison:
> Working chroot: Linux sodpro 5.3.9-300.fc31.x86_64 #1 SMP Wed Nov 6
> 16:13:19 UTC 2019 armv7l Linux
> Bare metal: Linux localhost 5.4.18-m300-alps-5 #1 PREEMPT Sat Feb 8
> 01:59:41 UTC 2020 armv5tel Linux

But it does seem to be related to target hardware. The one you have is
definitely older box (armv5tel). Perhaps you could show the
/proc/cpuinfo on it too?

But it does start to sound like the ARM boxes of the older kind and
does not support unaligned memory access. And seems to be giving
undefined behaviour instead of e.g. giving a trap.

Reviewing the code in apk, it seems that the murmur hashing code is not
properly accounting for alignment. So the symptoms do match. The hash
lookup does not work (well, works randomly based on few things), but
when enumerating all packages (by using the wildcard in lookups) it'll
show everything.

We have not really supported these old arm boxes. But perhaps it's
better to fix the murmur hash anyway. Or just use some other hash if
unaligned access does not work.

See: https://www.kernel.org/doc/Documentation/arm/mem_alignment

So to verify this, you could:
 echo 2 > /proc/cpu/alignment

If things start to work magically, it's the alignment issue. To verify
that no other program is suffering from this, you probably want initial
testing runs to be done using:
 echo 4 > /proc/cpu/alignment

That causes application to be killed with SIGBUS when it's trying to
access unaligned data.

Cheers,
Timo