From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Eric Biggers <ebiggers@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Netdev <netdev@vger.kernel.org>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
David Miller <davem@davemloft.net>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Samuel Neves <sneves@dei.uc.pt>,
Andrew Lutomirski <luto@kernel.org>,
Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>
Subject: Re: [PATCH net-next v5 07/20] zinc: Poly1305 generic C implementations and selftest
Date: Wed, 19 Sep 2018 03:35:15 +0200 [thread overview]
Message-ID: <CAHmME9oL98adRp6xXqaXxA0E4Oa4ecPW+JHChCS3hTgH7RLPjA@mail.gmail.com> (raw)
In-Reply-To: <20180919005054.GC74746@gmail.com>
On Wed, Sep 19, 2018 at 2:50 AM Eric Biggers <ebiggers@kernel.org> wrote:
> Hardcoding the 'input' array to 600 bytes forces the full amount of space to be
> reserved in the kernel image for every test vector. Also, if anyone adds a
> longer test vector they will need to remember to increase the value.
>
> It should be a const pointer instead, like the test vectors in crypto/testmgr.h.
I know. The agony. This has been really annoying me. I originally did
it the right way, but removed it last week, when I noticed that gcc
failed to put it in the initconst section:
https://git.zx2c4.com/WireGuard/commit/?id=f4698d20f13946afc6ce99e98685ba3f9adc4474
Even changing the (u8[]){ ... } into a (const u8[]){ ... } or even
into a const string literal does not do the trick. It makes it into
the constant data section with const, but it does not make it into the
initconst section. What a bummer.
I went asking about this on the gcc mailing list, to see if there was
just some aspect of C that I had overlooked:
https://gcc.gnu.org/ml/gcc/2018-09/msg00043.html So far, it looks like
we're SOL. I could probably make some macros to do this in a .S file
but... that's pretty unacceptably gross. Or I could define lots and
lots of variables in __initconst, and then connect them all together
at the end, but that's pretty gross too. Or I could have all this data
in one variable and record offsets into it, but that's even more
atrocious.
So I think it comes down to these two non-ugly options:
- We use fixed sized buffers, waste a lot of space, and be happy that
it's cleared from memory immediately after init/insertion anyway, so
it's not actually wasting ram.
- We use const string literals / constant compound literals, save
space on disk, but not benefit from having it cleared from memory
after init/insertion.
Of these, which would you prefer? I can see the argument both ways,
but in the end opted for the first. Or perhaps you have a better third
option?
Jason
next prev parent reply other threads:[~2018-09-19 1:35 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-18 16:16 [PATCH net-next v5 00/20] WireGuard: Secure Network Tunnel Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 01/20] asm: simd context helper API Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 02/20] zinc: introduce minimal cryptography library Jason A. Donenfeld
2018-09-20 15:41 ` Ard Biesheuvel
2018-09-20 16:01 ` Andy Lutomirski
2018-09-20 16:02 ` Arnd Bergmann
2018-09-21 0:11 ` Jason A. Donenfeld
2018-09-21 3:12 ` Andrew Lunn
2018-09-21 3:16 ` Jason A. Donenfeld
2018-09-21 3:23 ` Andy Lutomirski
2018-09-21 4:15 ` Jason A. Donenfeld
2018-09-21 4:30 ` Ard Biesheuvel
2018-09-21 4:32 ` Jason A. Donenfeld
2018-09-21 4:52 ` Andy Lutomirski
2018-09-22 16:11 ` Arnd Bergmann
2018-09-25 7:18 ` Arnd Bergmann
2018-09-25 14:29 ` Jason A. Donenfeld
2018-09-21 0:17 ` Jason A. Donenfeld
2018-09-25 10:25 ` Ard Biesheuvel
2018-09-25 14:44 ` Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 03/20] zinc: ChaCha20 generic C implementation and selftest Jason A. Donenfeld
2018-09-19 1:08 ` Eric Biggers
2018-09-19 2:02 ` Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 04/20] zinc: ChaCha20 x86_64 implementation Jason A. Donenfeld
2018-09-18 22:29 ` Thomas Gleixner
2018-09-19 2:14 ` Jason A. Donenfeld
2018-09-19 6:13 ` Thomas Gleixner
2018-09-19 11:33 ` Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 05/20] zinc: ChaCha20 ARM and ARM64 implementations Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 06/20] zinc: ChaCha20 MIPS32r2 implementation Jason A. Donenfeld
2018-09-18 20:25 ` Paul Burton
2018-09-20 13:19 ` Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 07/20] zinc: Poly1305 generic C implementations and selftest Jason A. Donenfeld
2018-09-19 0:50 ` Eric Biggers
2018-09-19 1:35 ` Jason A. Donenfeld [this message]
2018-09-19 4:13 ` Andy Lutomirski
2018-09-19 11:50 ` Jason A. Donenfeld
2018-09-19 12:26 ` Jason A. Donenfeld
2018-09-19 1:39 ` Jason A. Donenfeld
2018-09-19 1:41 ` Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 08/20] zinc: Poly1305 x86_64 implementation Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 09/20] zinc: Poly1305 ARM and ARM64 implementations Jason A. Donenfeld
2018-09-18 22:55 ` Eric Biggers
2018-09-19 0:17 ` Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 10/20] zinc: Poly1305 MIPS32r2 and MIPS64 implementations Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 11/20] zinc: ChaCha20Poly1305 construction and selftest Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 12/20] zinc: BLAKE2s generic C implementation " Jason A. Donenfeld
2018-09-19 0:41 ` Eric Biggers
2018-09-19 0:45 ` Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 13/20] zinc: BLAKE2s x86_64 implementation Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 14/20] zinc: Curve25519 generic C implementations and selftest Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 15/20] zinc: Curve25519 x86_64 implementation Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 16/20] zinc: Curve25519 ARM implementation Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 17/20] crypto: port Poly1305 to Zinc Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 18/20] crypto: port ChaCha20 " Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 19/20] security/keys: rewrite big_key crypto to use Zinc Jason A. Donenfeld
2018-09-18 16:16 ` [PATCH net-next v5 20/20] net: WireGuard secure network tunnel Jason A. Donenfeld
2018-09-18 23:34 ` Andrew Lunn
2018-09-19 2:04 ` Jason A. Donenfeld
2018-09-19 12:38 ` Andrew Lunn
2018-09-18 17:01 ` [PATCH net-next v5 19/20] security/keys: rewrite big_key crypto to use Zinc David Howells
2018-09-18 17:12 ` Jason A. Donenfeld
2018-09-18 18:28 ` [PATCH net-next v5 00/20] WireGuard: Secure Network Tunnel Ard Biesheuvel
2018-09-18 21:01 ` Jason A. Donenfeld
2018-09-19 17:21 ` Ard Biesheuvel
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