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From: David Marchand <david.marchand@redhat.com>
Date: Thu, 7 Apr 2022 17:24:07 +0200
Message-ID: <CAJFAV8yxK-qqQtNLrNFqyo1T+6qTSGfotSGufgR1SOY1muMzdg@mail.gmail.com>
Subject: Re: [PATCH v7] eal: fix rte_memcpy strict aliasing/alignment bugs
To: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>,
Luc Pelletier <lucp.at.work@gmail.com>
Cc: "Richardson, Bruce" <bruce.richardson@intel.com>,
"dev@dpdk.org" <dev@dpdk.org>,
"Li, Xiaoyun" <xiaoyun.li@intel.com>, "stable@dpdk.org" <stable@dpdk.org>,
Aaron Conole <aconole@redhat.com>, Owen Hilyard <ohilyard@iol.unh.edu>
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On Thu, Mar 10, 2022 at 3:55 PM Ananyev, Konstantin
<konstantin.ananyev@intel.com> wrote:
> > Calls to rte_memcpy for 1 < n < 16 could result in unaligned
> > loads/stores, which is undefined behaviour according to the C
> > standard, and strict aliasing violations.
> >
> > The code was changed to use a packed structure that allows aliasing
> > (using the __may_alias__ attribute) to perform the load/store
> > operations. This results in code that has the same performance as the
> > original code and that is also C standards-compliant.
> >
> > Fixes: d35cc1fe6a7a ("eal/x86: revert select optimized memcpy at run-time")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Luc Pelletier <lucp.at.work@gmail.com>
> Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
> Tested-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
Thanks, applied.
> As a side note, we probably need to check other similar places in DPDK code.
What would be the best way to detect those problematic places?
I tried UBsan, and it did report some of the issues fixed with this patch.
--
David Marchand