Are there SPARC [or other] aligned memory access requirements to avoid exceptions? [now that 11.0's armv6/v7 is allowing more unaligned accesses]

Mark Millard markmi at dsl-only.net
Thu May 26 22:03:35 UTC 2016


Is is safe to interpret that an rpi2 armv7/cortex-a7 unaligned access failure [from before -r300694] would (likely?) also be a failure on some forms of FreeBSD SPARC use?


Why I ask:

One of the ports that I had submitted a bug report for unaligned access problems on a rpi2 (armv7-a/cortex-a7 style handling) was:

archivers/lzo2

( https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=207096 ). I'd recently commented that the report might go away after testing what is now -r300694 (allowing more unaligned access on, for example, armv7-a/cortex-a7).

Matthias Andree has since asked in a comment:

> ISTR SPARC architectures also barf on unaligned access, so is it worth bothering the upstream author?

I have generally stuck to architectures for which I have examples to observe, if nothing else than to validate at least some of my understanding that is from reading materials. I normally only submit what I've observed in some form.

I've no such SPARC context nor do I have knowledge/reference material for SPARCs. Nor am I familiar with the choices FreeBSD may have made for SPARC configuration coverage.

As a matter of hear-say my impression is that some SPARCs can be configured to require some variation of strict alignment.

But I do not know how much I can infer from what I observed on a rpi2 (armv7-a/cortex-a7) to FreeBSD SPARC use getting similar results for at least come configurations. Nor do I have access to a test environment for SPARC.

So I wonder if my archivers/lzo2 submittal in question should survive because of SPARC even if the problem is validated to go away for the updated rpi2 like contexts (with armv7-a/cortex-a7 tailoring possibly involved). I have some other submittals that might face the same type of question.

===
Mark Millard
markmi at dsl-only.net



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