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Date:      Tue, 3 Jun 2025 11:01:31 +0200
From:      Robert Clausecker <fuz@freebsd.org>
To:        Shawn Webb <shawn.webb@hardenedbsd.org>
Cc:        Robert Clausecker <fuz@freebsd.org>, src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org
Subject:   Re: git: e698e4a53773 - main - lib/libmd: disable SHA1 AVX2 kernel
Message-ID:  <aD656_lqA2kJ8Ekh@fuz.su>
In-Reply-To: <iswwxq67opsuxidiehxizr7yg6em2obolcw2qx5d5rb2op5xij@wvozbns6esrt>
References:  <202506022333.552NX1uN061534@gitrepo.freebsd.org> <iswwxq67opsuxidiehxizr7yg6em2obolcw2qx5d5rb2op5xij@wvozbns6esrt>

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Hi Shawn,

Am Tue, Jun 03, 2025 at 12:17:26AM +0000 schrieb Shawn Webb:
> On Mon, Jun 02, 2025 at 11:33:01PM +0000, Robert Clausecker wrote:
> > The branch main has been updated by fuz:
> > 
> > URL: https://cgit.FreeBSD.org/src/commit/?id=e698e4a537736f6a7dd9a386e00997d7fb08e83f
> > 
> > commit e698e4a537736f6a7dd9a386e00997d7fb08e83f
> > Author:     Robert Clausecker <fuz@FreeBSD.org>
> > AuthorDate: 2025-06-02 22:54:32 +0000
> > Commit:     Robert Clausecker <fuz@FreeBSD.org>
> > CommitDate: 2025-06-02 23:27:00 +0000
> > 
> >     lib/libmd: disable SHA1 AVX2 kernel
> >     
> >     Seems like there is a bug lurking somewhere in the code.  This was not
> >     caught during my testing.  Disable the affected kernel for now while I
> >     figure out what is wrong with it.
> >     
> >     To reproduce, run
> >     
> >         jot -s '' -b 'a' -n 1000000 | sha1
> >     
> >     This should yield 34aa973cd4c4daa4f61eeb2bdbad27316534016f, but gives
> >     fe161a71d7941e3d63a9cacadc4f20716a721944 with the broken code.  Only the
> >     amd64/avx2 kernel is affected, the others seem to operate correctly.
> 
> Out of curiosity, how would one best determine whether they're
> affected? Would it be a part of the CPU features shown in
> /var/run/dmesg.boot?

You were affected if you had AVX2 but not SHA in your CPU features in
/var/run/dmesg.boot.  Thankfully, jrtc27@ seems to have found the transcription
errors in the code (see commit 207f3b2b25eaa0f9d32699e664b139e5e40e5450), so if
that's all that was wrong with it, I should be able to reenable it soon.

Yours,
Robert Clausecker

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