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Re: alignment errors on armel: what to do?

On 9/28/09, Daniel Kahn Gillmor <dkg@fifthhorseman.net> wrote:
>  after dealing with #548815, i'm a little bit concerned about the
>  behavior of the kernel in the face of alignment errors on armel.
>  i've read http://bugs.debian.org/397616 and followed the references in
>  there, so i think i understand why the default is to silently fail when
>  alignment errors happen.
>  However, it seems like we should still be filing bugs against packages
>  which trigger alignment errors, no?

>  i just turned on warnings in an NSLU2 running squeeze (a buildd for me)
>  and note alignment warnings from several processes:

>  should we be filing bugs for each of these?
Oh yes

> Should we be doing anything else?
Making unaligned accesses cause SIGBUS errors is even more
enlightening, though I wouldn't recommend it for a production machine.
For example, sid's apt-get is currently Bus erroring as soon as it
starts up, which makes things a little difficult...

An argument against enabling fixup is that it papers over bugs so they
remain undetected, while the fixup code is incredibly slow. A recent
example which should have run in under a second took three hours with
fixup enabled, which makes for programs that are silently and
invisibly much slower on ARM CPUs than usual.


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