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From: Florian Weimer <fweimer@redhat.com>
To: Noah Goldstein <goldstein.w.n@gmail.com>
Cc: Adhemerval Zanella <adhemerval.zanella@linaro.org>,
	 GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [PATCH v9 6/9] x86: Add AVX2 optimized chacha20
Date: Wed, 13 Jul 2022 22:16:00 +0200	[thread overview]
Message-ID: <87cze8zs3j.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <CAFUsyfKKu7ExiKVc6XDPvhJdROJpSshSBdW1hfXhsiW9s1VbxA@mail.gmail.com> (Noah Goldstein's message of "Wed, 13 Jul 2022 11:07:27 -0700")

* Noah Goldstein:

> Since `arc4random ()` might need to read from /dev/urandom I don't
> think this function could ever truly be RTM safe so we may not care.
>
> If im missing something we do want to support RTM, should there be a
> '!CPU_FEATURE_USABLE_P (cpu_features, RTM)' check for the avx2
> implementation?

Calling arc4random from a transaction is potentially unsafe anyway
because it may act as an oracle that reveals the internal PRNG state.
The application needs to avoid that.  I think we can use the AVX2
implementation even with RTM enabled.

Thanks,
Florian


  parent reply	other threads:[~2022-07-13 20:16 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-13 17:36 [PATCH v9 0/9] Add arc4random support Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 1/9] stdlib: Add arc4random, arc4random_buf, and arc4random_uniform (BZ #4417) Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 2/9] stdlib: Add arc4random tests Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 3/9] benchtests: Add arc4random benchtest Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 4/9] aarch64: Add optimized chacha20 Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 5/9] x86: Add SSE2 " Adhemerval Zanella
2022-07-13 18:12   ` Noah Goldstein
2022-07-13 18:20     ` Adhemerval Zanella Netto
2022-07-13 18:22       ` Noah Goldstein
2022-07-13 18:27         ` Noah Goldstein
2022-07-13 18:29           ` Adhemerval Zanella Netto
2022-07-13 18:53             ` Noah Goldstein
2022-07-13 17:36 ` [PATCH v9 6/9] x86: Add AVX2 " Adhemerval Zanella
2022-07-13 18:07   ` Noah Goldstein
2022-07-13 19:31     ` Adhemerval Zanella Netto
2022-07-13 20:24       ` Noah Goldstein
2022-07-13 20:16     ` Florian Weimer [this message]
2022-07-13 20:23       ` Noah Goldstein
2022-07-13 17:36 ` [PATCH v9 7/9] powerpc64: Add " Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 8/9] s390x: " Adhemerval Zanella
2022-07-13 17:36 ` [PATCH v9 9/9] manual: Add documentation for arc4random functions Adhemerval Zanella
2022-07-14 10:03   ` Mark Harris
2022-07-14 11:08     ` Adhemerval Zanella Netto

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