linux-kernel - Re: [PATCH] lib/int_sqrt.c: optimize for small argument values

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 for Android: free password hash cracker in your pocket

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

Message-ID: <1508480027.6806.44.camel@perches.com>
Date:   Thu, 19 Oct 2017 23:13:47 -0700
From:   Joe Perches <joe@...ches.com>
To:     Michael Davidson <md@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        David Miller <davem@...emloft.net>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Kees Cook <keescook@...omium.org>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lib/int_sqrt.c: optimize for small argument values

On Thu, 2017-10-19 at 13:31 -0700, Michael Davidson wrote:
> int_sqrt() currently takes approximately constant time
> regardless of the value of the argument. By using the
> magnitude of the operand to set the initial conditions
> for the calculation the cost becomes proportional to
> log2 of the argument with the worst case behavior not
> being measurably slower than it currently is.

https://lkml.org/lkml/2017/7/24/408