Return-Path: Received: from mail-it1-f196.google.com ([209.85.166.196]:53233 "EHLO mail-it1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728921AbeJWGpy (ORCPT ); Tue, 23 Oct 2018 02:45:54 -0400 Received: by mail-it1-f196.google.com with SMTP id 134-v6so13746800itz.2 for ; Mon, 22 Oct 2018 15:25:28 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20181022184236.GA59695@gmail.com> References: <20181015175424.97147-1-ebiggers@kernel.org> <20181015175424.97147-10-ebiggers@kernel.org> <20181020053834.GC876@sol.localdomain> <20181022184236.GA59695@gmail.com> From: Ard Biesheuvel Date: Mon, 22 Oct 2018 19:25:27 -0300 Message-ID: Subject: Re: [RFC PATCH v2 09/12] crypto: nhpoly1305 - add NHPoly1305 support To: Eric Biggers Cc: "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" , linux-fscrypt@vger.kernel.org, linux-arm-kernel , Linux Kernel Mailing List , Herbert Xu , Paul Crowley , Greg Kaiser , Michael Halcrow , "Jason A . Donenfeld" , Samuel Neves , Tomer Ashur Content-Type: text/plain; charset="UTF-8" Sender: linux-crypto-owner@vger.kernel.org List-ID: On 22 October 2018 at 15:42, Eric Biggers wrote: > On Sat, Oct 20, 2018 at 11:06:00PM +0800, Ard Biesheuvel wrote: >> >> > + >> >> > +#define NH_STRIDE(K0, K1, K2, K3) \ >> >> > +({ \ >> >> > + m_A = get_unaligned_le32(src); src += 4; \ >> >> > + m_B = get_unaligned_le32(src); src += 4; \ >> >> > + m_C = get_unaligned_le32(src); src += 4; \ >> >> > + m_D = get_unaligned_le32(src); src += 4; \ >> >> > + K3##_A = *key++; \ >> >> > + K3##_B = *key++; \ >> >> > + K3##_C = *key++; \ >> >> > + K3##_D = *key++; \ >> >> > + sum0 += (u64)(u32)(m_A + K0##_A) * (u32)(m_C + K0##_C); \ >> >> > + sum1 += (u64)(u32)(m_A + K1##_A) * (u32)(m_C + K1##_C); \ >> >> > + sum2 += (u64)(u32)(m_A + K2##_A) * (u32)(m_C + K2##_C); \ >> >> > + sum3 += (u64)(u32)(m_A + K3##_A) * (u32)(m_C + K3##_C); \ >> >> > + sum0 += (u64)(u32)(m_B + K0##_B) * (u32)(m_D + K0##_D); \ >> >> > + sum1 += (u64)(u32)(m_B + K1##_B) * (u32)(m_D + K1##_D); \ >> >> > + sum2 += (u64)(u32)(m_B + K2##_B) * (u32)(m_D + K2##_D); \ >> >> > + sum3 += (u64)(u32)(m_B + K3##_B) * (u32)(m_D + K3##_D); \ >> >> > +}) >> >> > + >> >> > +static void nh_generic(const u32 *key, const u8 *src, size_t srclen, >> >> > + __le64 hash[NH_NUM_PASSES]) >> >> > +{ >> >> > + u64 sum0 = 0, sum1 = 0, sum2 = 0, sum3 = 0; >> >> > + u32 k0_A = *key++; >> >> > + u32 k0_B = *key++; >> >> > + u32 k0_C = *key++; >> >> > + u32 k0_D = *key++; >> >> > + u32 k1_A = *key++; >> >> > + u32 k1_B = *key++; >> >> > + u32 k1_C = *key++; >> >> > + u32 k1_D = *key++; >> >> > + u32 k2_A = *key++; >> >> > + u32 k2_B = *key++; >> >> > + u32 k2_C = *key++; >> >> > + u32 k2_D = *key++; >> >> > + u32 k3_A, k3_B, k3_C, k3_D; >> >> > + u32 m_A, m_B, m_C, m_D; >> >> > + size_t n = srclen / NH_MESSAGE_UNIT; >> >> > + >> >> > + BUILD_BUG_ON(NH_PAIR_STRIDE != 2); >> >> > + BUILD_BUG_ON(NH_NUM_PASSES != 4); >> >> > + >> >> > + while (n >= 4) { >> >> > + NH_STRIDE(k0, k1, k2, k3); >> >> > + NH_STRIDE(k1, k2, k3, k0); >> >> > + NH_STRIDE(k2, k3, k0, k1); >> >> > + NH_STRIDE(k3, k0, k1, k2); >> >> > + n -= 4; >> >> > + } >> >> > + if (n) { >> >> > + NH_STRIDE(k0, k1, k2, k3); >> >> > + if (--n) { >> >> > + NH_STRIDE(k1, k2, k3, k0); >> >> > + if (--n) >> >> > + NH_STRIDE(k2, k3, k0, k1); >> >> > + } >> >> > + } >> >> > + >> >> >> >> This all looks a bit clunky to me, with the macro, the *key++s in the >> >> initializers and these conditionals. >> >> >> >> Was it written in this particular way to get GCC to optimize it in the >> >> right way? >> > >> > This does get compiled into something much faster than a naive version, which >> > you can find commented out at >> > https://github.com/google/adiantum/blob/master/benchmark/src/nh.c#L14. >> > >> > Though, I admit that I haven't put a ton of effort into this C implementation of >> > NH yet. Right now it's actually somewhat of a translation of the NEON version. >> > I'll do some experiments and see if it can be made into something less ugly >> > without losing performance. >> > >> >> No that's fine but please document it. >> > > Hmm, I'm actually leaning towards the following instead. Unrolling multiple > strides to try to reduce loads of the keys doesn't seem worthwhile in the C > implementation; for one, it bloats the code size a lot > (412 => 2332 bytes on arm32). > > static void nh_generic(const u32 *key, const u8 *message, size_t message_len, > __le64 hash[NH_NUM_PASSES]) > { > u64 sums[4] = { 0, 0, 0, 0 }; > > BUILD_BUG_ON(NH_PAIR_STRIDE != 2); > BUILD_BUG_ON(NH_NUM_PASSES != 4); > > while (message_len) { > u32 m0 = get_unaligned_le32(message + 0); > u32 m1 = get_unaligned_le32(message + 4); > u32 m2 = get_unaligned_le32(message + 8); > u32 m3 = get_unaligned_le32(message + 12); > > sums[0] += (u64)(u32)(m0 + key[ 0]) * (u32)(m2 + key[ 2]); > sums[1] += (u64)(u32)(m0 + key[ 4]) * (u32)(m2 + key[ 6]); > sums[2] += (u64)(u32)(m0 + key[ 8]) * (u32)(m2 + key[10]); > sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]); > sums[0] += (u64)(u32)(m1 + key[ 1]) * (u32)(m3 + key[ 3]); > sums[1] += (u64)(u32)(m1 + key[ 5]) * (u32)(m3 + key[ 7]); > sums[2] += (u64)(u32)(m1 + key[ 9]) * (u32)(m3 + key[11]); > sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]); Are these (u32) casts really necessary? All the addends are u32 types, so I'd expect each (x + y) subexpression to have a u32 type already as well. Or am I missing something? > key += NH_MESSAGE_UNIT / sizeof(key[0]); > message += NH_MESSAGE_UNIT; > message_len -= NH_MESSAGE_UNIT; > } > > hash[0] = cpu_to_le64(sums[0]); > hash[1] = cpu_to_le64(sums[1]); > hash[2] = cpu_to_le64(sums[2]); > hash[3] = cpu_to_le64(sums[3]); > } In any case, this looks much better to me, so if the performance is satisfactory, let's use this version.