linux-kernel - RE: [PATCH v3] random: handle archrandom with multiple longs

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Message-ID: <10561a841a7342c882aabb0fbdbfc762@AcuMS.aculab.com>
Date:   Mon, 25 Jul 2022 09:36:34 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "'Jason A. Donenfeld'" <Jason@...c4.com>,
        Borislav Petkov <bp@...e.de>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>, Will Deacon <will@...nel.org>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        "Catalin Marinas" <catalin.marinas@....com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Johannes Berg <johannes@...solutions.net>,
        Mark Rutland <mark.rutland@....com>,
        Harald Freudenberger <freude@...ux.ibm.com>,
        "Michael Ellerman" <mpe@...erman.id.au>
Subject: RE: [PATCH v3] random: handle archrandom with multiple longs

...
> More directly, the reason we don't want to error is because the use case
> has fallbacks meant to handle errors. The cascade looks like this
> (quoting from the other email):
> 
>     unsigned long array[whatever];
>     for (i = 0; i < ARRAY_SIZE(array);) {
>         longs = arch_get_random_seed_longs(&array[i], ARRAY_SIZE(array) - i);
>         if (longs) {
>             i += longs;
>             continue;
>         }
>         longs = arch_get_random_longs(&array[i], ARRAY_SIZE(array) - i);
>         if (longs) {
>             i += longs;
>             continue;
>         }
>         array[i++] = random_get_entropy();
>     }
> 
> It tries to get the best that it can as much as it can, but isn't going
> to block or do anything too nuts for that.

Do you really want to retry the earlier calls that returned no data?

	David

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