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From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Ard Biesheuvel <ard.biesheuvel@linaro.org>
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 16:13:53 +0200	[thread overview]
Message-ID: <CAHmME9o5hHERnrT_V2EmL9GYRNGpOyos1pmwUHN71vt8yPb+ow@mail.gmail.com> (raw)
In-Reply-To: <20191007164610.6881-25-ard.biesheuvel@linaro.org>

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.

Jason

  reply	other threads:[~2019-10-14 14:14 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 [this message]
2019-10-14 16:07     ` Ard Biesheuvel
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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