linux-kernel - Re: [PATCH v2 0/7] crypto: sha256 - Merge 2 separate C implementations into 1, put into separate library

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Date:   Mon, 19 Aug 2019 23:30:16 +0300
From:   Ard Biesheuvel <ard.biesheuvel@...aro.org>
To:     Hans de Goede <hdegoede@...hat.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Eric Biggers <ebiggers@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        linux-s390 <linux-s390@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 0/7] crypto: sha256 - Merge 2 separate C
 implementations into 1, put into separate library

On Mon, 19 Aug 2019 at 22:38, Hans de Goede <hdegoede@...hat.com> wrote:
>
> Hi,
>
> On 19-08-19 17:08, Ard Biesheuvel wrote:
> > On Sat, 17 Aug 2019 at 17:24, Hans de Goede <hdegoede@...hat.com> wrote:
> >>
> >> Hi All,
> >>
> >> Here is v2 of my patch series refactoring the current 2 separate SHA256
> >> C implementations into 1 and put it into a separate library.
> >>
> >> There are 3 reasons for this:
> >>
> >> 1) Remove the code duplication of having 2 separate implementations
> >>
> >> 2) Offer a separate library SHA256 implementation which can be used
> >> without having to call crypto_alloc_shash first. This is especially
> >> useful for use during early boot when crypto_alloc_shash does not
> >> work yet.
> >>
> >> 3) Having the purgatory code using the same code as the crypto subsys means
> >> that the purgratory code will be tested by the crypto subsys selftests.
> >>
> >> This has been tested on x86, including checking that kecec still works.
> >>
> >> This has NOT been tested on s390, if someone with access to s390 can
> >> test that things still build with this series applied and that
> >> kexec still works, that would be great.
> >>
> >> Changes in v2:
> >> - Use put_unaligned_be32 to store the hash to allow callers to use an
> >>    unaligned buffer for storing the hash
> >> - Add a comment to include/crypto/sha256.h explaining that these functions
> >>    now may be used outside of the purgatory too (and that using the crypto
> >>    API instead is preferred)
> >> - Add sha224 support to the lib/crypto/sha256 library code
> >> - Make crypto/sha256_generic.c not only use sha256_transform from
> >>    lib/crypto/sha256.c but also switch it to using sha256_init, sha256_update
> >>    and sha256_final from there so that the crypto subsys selftests fully test
> >>    the lib/crypto/sha256.c implementation
> >>
> >
> > This looks fine to me, although I agree with Eric's feedback regarding
> > further cleanups.
>
> Ack, as I already told Eric I'm happy to do a follow up series with
> the necessary local static function renames so that we can then merge
> sha256.h into sha.h .
>

Yes, that would be excellent.

> > Also, now that we have a C library, I'd like to drop
> > the dependency of the mips and x86 sha256 algo implementations up
> > sha256_generic.c, and use the library directly instead (so that
> > sha256-generic is no longer needed on x86 or mips)
>
> I assume this is more of a generic remark and not targeted towards me?
>

Let's call it a general call for volunteers :-)