lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <17cd289430f08f2b75b7f04242c646f6@mailhost.ics.forth.gr> Date: Tue, 22 Jun 2021 04:07:47 +0300 From: Nick Kossifidis <mick@....forth.gr> To: Matteo Croce <mcroce@...ux.microsoft.com> Cc: linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org, Paul Walmsley <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, Atish Patra <atish.patra@....com>, Emil Renner Berthing <kernel@...il.dk>, Akira Tsukamoto <akira.tsukamoto@...il.com>, Drew Fustini <drew@...gleboard.org>, Bin Meng <bmeng.cn@...il.com>, David Laight <David.Laight@...lab.com>, Guo Ren <guoren@...nel.org> Subject: Re: [PATCH v3 3/3] riscv: optimized memset Στις 2021-06-17 18:27, Matteo Croce έγραψε: > + > +void *__memset(void *s, int c, size_t count) > +{ > + union types dest = { .u8 = s }; > + > + if (count >= MIN_THRESHOLD) { > + const int bytes_long = BITS_PER_LONG / 8; You could make 'const int bytes_long = BITS_PER_LONG / 8;' and 'const int mask = bytes_long - 1;' from your memcpy patch visible to memset as well (static const...) and use them here (mask would make more sense to be named as word_mask). > + unsigned long cu = (unsigned long)c; > + > + /* Compose an ulong with 'c' repeated 4/8 times */ > + cu |= cu << 8; > + cu |= cu << 16; > +#if BITS_PER_LONG == 64 > + cu |= cu << 32; > +#endif > + You don't have to create cu here, you'll fill dest buffer with 'c' anyway so after filling up enough 'c's to be able to grab an aligned word full of them from dest, you can just grab that word and keep filling up dest with it. > +#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS > + /* Fill the buffer one byte at time until the destination > + * is aligned on a 32/64 bit boundary. > + */ > + for (; count && dest.uptr % bytes_long; count--) You could reuse & mask here instead of % bytes_long. > + *dest.u8++ = c; > +#endif I noticed you also used CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS on your memcpy patch, is it worth it here ? To begin with riscv doesn't set it and even if it did we are talking about a loop that will run just a few times to reach the alignment boundary (worst case scenario it'll run 7 times), I don't think we gain much here, even for archs that have efficient unaligned access.
Powered by blists - more mailing lists