linux-kernel - Re: [PATCH RFC v1] random: implement getrandom() in vDSO

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Message-ID: <CAHmME9pNN6Pc_1NaMDv+hqv_ULXiVUYFXM=Xigu_StvGS_-53A@mail.gmail.com>
Date:   Tue, 2 Aug 2022 17:26:05 +0200
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        X86 ML <x86@...nel.org>, Nadia Heninger <nadiah@...ucsd.edu>,
        Thomas Ristenpart <ristenpart@...nell.edu>,
        "Theodore Ts'o" <tytso@....edu>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Adhemerval Zanella Netto <adhemerval.zanella@...aro.org>,
        Florian Weimer <fweimer@...hat.com>
Subject: Re: [PATCH RFC v1] random: implement getrandom() in vDSO

Hi Thomas,

On Tue, Aug 2, 2022 at 5:14 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> Seriously no.

Why so serious all at once? :-)

> All existing VDSO functions have exactly the same function
> signature and semantics as their syscall counterparts. So they are drop
> in equivalent.
>
> But:
>
>   ssize_t getrandom(void *, void *, size_t, unsigned int);
>
> is very much different than
>
>   ssize_t getrandom(void *, size_t, unsigned int);
>
> Different signature and different semantics.

Different signature, but basically the same semantics.

> So you have to go through the whole process of a new ABI whether you
> like it or not.

Ahh, in that sense. Yea, I'd rather not have to do that too, with the
additional opaque handle passed as the first argument. It'd be nice if
there were some private place where I could store the necessary state,
but I'm not really sure where that might be at the moment. If you have
any ideas, please let me know.

Jason