linux-kernel - Re: [PATCH v12 0/6] implement getrandom() in vDSO

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Date:   Wed, 21 Dec 2022 15:25:49 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "patches@...ts.linux.dev" <patches@...ts.linux.dev>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Adhemerval Zanella Netto <adhemerval.zanella@...aro.org>,
        Carlos O'Donell <carlos@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        Arnd Bergmann <arnd@...db.de>, Jann Horn <jannh@...gle.com>,
        Christian Brauner <brauner@...nel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v12 0/6] implement getrandom() in vDSO

On Tue, Dec 20, 2022 at 08:13:14PM +0000, Eric Biggers wrote:
> On Tue, Dec 20, 2022 at 05:17:52PM +0000, Christophe Leroy wrote:
> > Hi Jason,
> > 
> > Le 12/12/2022 à 19:53, Jason A. Donenfeld a écrit :
> > > Changes v11->v12:
> > > ----------------
> > > - In order to avoid mlock()ing pages, and the related rlimit and fork
> > >    inheritance issues there, Introduce VM_DROPPABLE to prevent swapping
> > >    while meeting the cache-like requirements of vDSO getrandom().
> > > 
> > >    This has some tenticles in mm/ and arch/x86/ code, so I've marked the
> > >    two patches for that as still RFC, while the rest of the series is not
> > >    RFC.
> > > 
> > > - Mandate that opaque state blobs don't straddle page boundaries, so
> > >    that VM_DROPPABLE can work on page-level granularity rather than
> > >    allocation-level granularity.
> > > 
> > > - Add compiler barriers to vDSO getrandom() to prevent theoretical
> > >    reordering potential.
> > > 
> > > - Initialize the trials loop counter in the chacha test.
> > 
> > I would have liked to give it a try on powerpc, but the series 
> > conflicts. I tried both on v6.1 and on linus/master from now:
> > 
> 
> Same here, I can't figure out how to apply this series.

Rebased v13 posted: https://lore.kernel.org/all/20221221142327.126451-1-Jason@zx2c4.com/

Jason