linux-kernel - Re: [PATCH] lib/crypto: blake2s: avoid indirect calls to compression function for Clang CFI

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Date:   Fri, 21 Jan 2022 12:51:40 -0800
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Eric Biggers <ebiggers@...nel.org>,
        Miles Chen <miles.chen@...iatek.com>,
        Ard Biesheuvel <ardb@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC..." 
        <linux-mediatek@...ts.infradead.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH] lib/crypto: blake2s: avoid indirect calls to compression
 function for Clang CFI

Hi Jason,

On Fri, Jan 21, 2022 at 12:23 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
>
> On Fri, Jan 21, 2022 at 8:54 PM Eric Biggers <ebiggers@...nel.org> wrote:
> > There are some lines over 80 columns in this patch.
>
> I'll fix that up.
>
> > Otherwise this looks fine.  It would be really nice to fix this in clang,
> > though.
>
> I agree. I'm wondering whether it makes sense to roll with this patch,
> or to just not change anything and lean on Clang upstream to fix their
> bug. Full LTO is marked as "experimental" still. On the other hand,
> Android ships with it turned on, so how "experimental" can it really
> be? I don't have a strong read on the Clang ecosystem to know what
> makes most sense, to apply this or not. Do you have an opinion?

We'll work on fixing the compiler, but please note that it's most
likely going to take a while, so I would prefer to work around the
issue in the kernel for now.

Sami