From: "Theodore Ts'o" <tytso@mit.edu>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
Hannes Frederic Sowa <hannes@stressinduktion.org>,
Andy Lutomirski <luto@amacapital.net>
Subject: Re: [PATCH 1/2] random: use chacha20 for get_random_int/long
Date: Fri, 20 Jan 2017 19:10:13 -0500 [thread overview]
Message-ID: <20170121001013.6vtxpuaqplwnvwaz@thunk.org> (raw)
In-Reply-To: <CAHmME9oRZ-uNy-p5EMOULcQd9iz1i+FHhTtTB8czQqF=ZKxt3A@mail.gmail.com>
On Fri, Jan 20, 2017 at 04:38:59PM +0100, Jason A. Donenfeld wrote:
> I was thinking that the issue isn't merely cache line and a slow down,
> but that on some platforms, this could be an _illegal unaligned
> access_. That means we'd need to rewrite the code to use the unaligned
> access helpers or memcpy, and then it's really suboptimal, not to
> mention ugly, since just indexing into an array like we do now is so
> clean.
Why would there be an unaligned access? What I was suggesting was an
array of u32, and we just do two separate u32 accesses with a shift in
the case of get_random_u64. There's nothing illegal about that.
u64 retval;
retval = (array[pointer] << 32) + array[pointer+1];
pointer += 2;
This is not terribly suboptimal nor terribly ugly.
- Ted
next prev parent reply other threads:[~2017-01-21 0:10 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-06 18:32 [PATCH 1/2] random: use chacha20 for get_random_int/long Jason A. Donenfeld
2017-01-06 18:32 ` [PATCH 2/2] random: convert get_random_int/long into get_random_u32/u64 Jason A. Donenfeld
2017-01-18 3:49 ` [PATCH 1/2] random: use chacha20 for get_random_int/long Theodore Ts'o
2017-01-20 5:27 ` Jason A. Donenfeld
2017-01-20 14:28 ` Theodore Ts'o
2017-01-20 15:38 ` Jason A. Donenfeld
2017-01-21 0:10 ` Theodore Ts'o [this message]
2017-01-21 0:13 ` Jason A. Donenfeld
2017-01-20 15:47 ` Jason A. Donenfeld
2017-01-21 0:15 ` Theodore Ts'o
2017-01-21 0:16 ` Jason A. Donenfeld
2017-01-21 6:24 ` Theodore Ts'o
2017-01-21 14:08 ` Jason A. Donenfeld
2017-01-22 11:24 ` Greg Kroah-Hartman
2017-01-22 12:21 ` Jason A. Donenfeld
2017-01-22 15:20 ` Greg Kroah-Hartman
2017-01-22 15:34 ` Jason A. Donenfeld
2017-01-22 15:34 ` [PATCH 2/2] random: convert get_random_int/long into get_random_u32/u64 Jason A. Donenfeld
2017-01-22 22:28 ` [PATCH 1/2] random: use chacha20 for get_random_int/long Theodore Ts'o
2017-01-22 22:49 ` Jason A. Donenfeld
2017-01-23 0:33 ` Theodore Ts'o
2017-01-23 8:12 ` Greg Kroah-Hartman
-- strict thread matches above, loose matches on Subject: below --
2016-12-22 18:07 Jason A. Donenfeld
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