linux-kernel - [PATCH v2 0/3] lib/string: optimized mem* functions

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210702123153.14093-1-mcroce@linux.microsoft.com>
Date:   Fri,  2 Jul 2021 14:31:50 +0200
From:   Matteo Croce <mcroce@...ux.microsoft.com>
To:     linux-kernel@...r.kernel.org, Nick Kossifidis <mick@....forth.gr>,
        Guo Ren <guoren@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        David Laight <David.Laight@...lab.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Emil Renner Berthing <kernel@...il.dk>,
        Drew Fustini <drew@...gleboard.org>
Cc:     linux-arch@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-riscv@...ts.infradead.org
Subject: [PATCH v2 0/3] lib/string: optimized mem* functions

From: Matteo Croce <mcroce@...rosoft.com>

Rewrite the generic mem{cpy,move,set} so that memory is accessed with
the widest size possible, but without doing unaligned accesses.

This was originally posted as C string functions for RISC-V[1], but as
there was no specific RISC-V code, it was proposed for the generic
lib/string.c implementation.

Tested on RISC-V and on x86_64 by undefining __HAVE_ARCH_MEM{CPY,SET,MOVE}
and HAVE_EFFICIENT_UNALIGNED_ACCESS.

These are the performances of memcpy() and memset() of a RISC-V machine
on a 32 mbyte buffer:

memcpy:
original aligned:	 75 Mb/s
original unaligned:	 75 Mb/s
new aligned:		114 Mb/s
new unaligned:		107 Mb/s

memset:
original aligned:	140 Mb/s
original unaligned:	140 Mb/s
new aligned:		241 Mb/s
new unaligned:		241 Mb/s

The size increase is negligible:

$ scripts/bloat-o-meter vmlinux.orig vmlinux
add/remove: 0/0 grow/shrink: 4/1 up/down: 427/-6 (421)
Function                                     old     new   delta
memcpy                                        29     351    +322
memset                                        29     117     +88
strlcat                                       68      78     +10
strlcpy                                       50      57      +7
memmove                                       56      50      -6
Total: Before=8556964, After=8557385, chg +0.00%

These functions will be used for RISC-V initially.

[1] https://lore.kernel.org/linux-riscv/20210617152754.17960-1-mcroce@linux.microsoft.com/

Matteo Croce (3):
  lib/string: optimized memcpy
  lib/string: optimized memmove
  lib/string: optimized memset

 lib/string.c | 130 ++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 113 insertions(+), 17 deletions(-)

-- 
2.31.1