From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
David Miller <davem@davemloft.net>,
Samuel Neves <sneves@dei.uc.pt>, Arnd Bergmann <arnd@arndb.de>,
Eric Biggers <ebiggers@google.com>,
Andy Lutomirski <luto@kernel.org>,
Martin Willi <martin@strongswan.org>,
Rene van Dorst <opensource@vdorst.com>
Subject: Re: [PATCH v3 24/29] crypto: lib/curve25519 - work around Clang stack spilling issue
Date: Mon, 14 Oct 2019 18:07:15 +0200 [thread overview]
Message-ID: <CAKv+Gu-b1gSoG0kc=yzfUE-j7vjZOo=JpD64dF6Lm8+eZruFbw@mail.gmail.com> (raw)
In-Reply-To: <CAHmME9o5hHERnrT_V2EmL9GYRNGpOyos1pmwUHN71vt8yPb+ow@mail.gmail.com>
On Mon, 14 Oct 2019 at 16:14, Jason A. Donenfeld <Jason@zx2c4.com> wrote:
>
> Hi Ard,
>
> On Mon, Oct 7, 2019 at 6:46 PM Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> > Arnd reports that the 32-bit generic library code for Curve25119 ends
> > up using an excessive amount of stack space when built with Clang:
> >
> > lib/crypto/curve25519-fiat32.c:756:6: error: stack frame size
> > of 1384 bytes in function 'curve25519_generic'
> > [-Werror,-Wframe-larger-than=]
> >
> > Let's give some hints to the compiler regarding which routines should
> > not be inlined, to prevent it from running out of registers and spilling
> > to the stack. The resulting code performs identically under both GCC
> > and Clang, and makes the warning go away.
>
> Are you *sure* about that? Couldn't we fix clang instead? I'd rather
> fixes go there instead of gimping this. The reason is that I noticed
> before that this code, performance-wise, was very inlining sensitive.
> Can you benchmark this on ARM32-noneon and on MIPS32? If there's a
> performance difference there, then maybe you can defer this part of
> the series until after the rest lands, and then we'll discuss at
> length various strategies? Alternatively, if you benchmark those and
> it also makes no difference, then it indeed makes no difference.
>
I tested this using a 32-bit ARM VM running under an 64-bit KVM
hypervisor, doing 100 iterations of the selftest.
next prev parent reply other threads:[~2019-10-14 16:07 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-07 16:45 [PATCH v3 00/29] crypto: crypto API library interfaces for WireGuard Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 01/29] crypto: chacha - move existing library code into lib/crypto Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 02/29] crypto: x86/chacha - depend on generic chacha library instead of crypto driver Ard Biesheuvel
2019-10-11 6:00 ` Eric Biggers
2019-10-15 10:00 ` Martin Willi
2019-10-15 10:12 ` Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 03/29] crypto: x86/chacha - expose SIMD ChaCha routine as library function Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 04/29] crypto: arm64/chacha - depend on generic chacha library instead of crypto driver Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 05/29] crypto: arm64/chacha - expose arm64 ChaCha routine as library function Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 06/29] crypto: arm/chacha - import Eric Biggers's scalar accelerated ChaCha code Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 07/29] crypto: arm/chacha - remove dependency on generic ChaCha driver Ard Biesheuvel
2019-10-11 6:12 ` Eric Biggers
2019-10-11 6:31 ` Eric Biggers
2019-10-07 16:45 ` [PATCH v3 08/29] crypto: arm/chacha - expose ARM ChaCha routine as library function Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 09/29] crypto: mips/chacha - import 32r2 ChaCha code from Zinc Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 10/29] crypto: mips/chacha - wire up accelerated 32r2 " Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 11/29] crypto: chacha - unexport chacha_generic routines Ard Biesheuvel
2019-10-11 6:04 ` Eric Biggers
2019-10-07 16:45 ` [PATCH v3 12/29] crypto: poly1305 - move core routines into a separate library Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 13/29] crypto: x86/poly1305 - unify Poly1305 state struct with generic code Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 14/29] crypto: poly1305 - expose init/update/final library interface Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 15/29] crypto: x86/poly1305 - depend on generic library not generic shash Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 16/29] crypto: x86/poly1305 - expose existing driver as poly1305 library Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 17/29] crypto: arm64/poly1305 - incorporate OpenSSL/CRYPTOGAMS NEON implementation Ard Biesheuvel
2019-10-07 16:45 ` [PATCH v3 18/29] crypto: arm/poly1305 " Ard Biesheuvel
2019-10-07 16:46 ` [PATCH v3 19/29] crypto: mips/poly1305 - incorporate OpenSSL/CRYPTOGAMS optimized implementation Ard Biesheuvel
2019-10-07 21:02 ` René van Dorst
2019-10-08 5:55 ` Ard Biesheuvel
2019-10-08 11:38 ` Andy Polyakov
2019-10-08 17:46 ` René van Dorst
2019-10-11 14:14 ` Andy Polyakov
2019-10-11 17:21 ` René van Dorst
2019-10-11 18:49 ` Andy Polyakov
2019-10-11 21:38 ` Arnd Bergmann
2019-10-07 16:46 ` [PATCH v3 20/29] int128: move __uint128_t compiler test to Kconfig Ard Biesheuvel
2019-10-07 16:46 ` [PATCH v3 21/29] crypto: BLAKE2s - generic C library implementation and selftest Ard Biesheuvel
2019-10-11 6:02 ` Eric Biggers
2019-10-11 16:45 ` Jason A. Donenfeld
2019-10-14 12:53 ` Ard Biesheuvel
2019-10-07 16:46 ` [PATCH v3 22/29] crypto: BLAKE2s - x86_64 library implementation Ard Biesheuvel
2019-10-07 16:46 ` [PATCH v3 23/29] crypto: Curve25519 - generic C library implementations and selftest Ard Biesheuvel
2019-10-07 16:46 ` [PATCH v3 24/29] crypto: lib/curve25519 - work around Clang stack spilling issue Ard Biesheuvel
2019-10-14 14:13 ` Jason A. Donenfeld
2019-10-14 16:07 ` Ard Biesheuvel [this message]
2019-10-07 16:46 ` [PATCH v3 25/29] crypto: Curve25519 - x86_64 library implementation Ard Biesheuvel
2019-10-07 16:46 ` [PATCH v3 26/29] crypto: arm - import Bernstein and Schwabe's Curve25519 ARM implementation Ard Biesheuvel
2019-10-07 16:46 ` [PATCH v3 27/29] crypto: arm/Curve25519 - wire up NEON implementation Ard Biesheuvel
2019-10-07 16:46 ` [PATCH v3 28/29] crypto: chacha20poly1305 - import construction and selftest from Zinc Ard Biesheuvel
2019-10-11 6:14 ` Eric Biggers
2019-10-07 16:46 ` [PATCH v3 29/29] crypto: lib/chacha20poly1305 - reimplement crypt_from_sg() routine Ard Biesheuvel
2019-10-14 14:33 ` [PATCH v3 00/29] crypto: crypto API library interfaces for WireGuard Jason A. Donenfeld
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