linux-kernel - Re: [PATCH] crypto: make michael

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Date:	Fri, 16 May 2008 08:52:03 -0700
From:	Harvey Harrison <harvey.harrison@...il.com>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Sebastian Siewior <lkml@...breakpoint.cc>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] crypto: make michael_block a function

On Fri, 2008-05-16 at 10:10 +0200, Johannes Berg wrote:
> On Fri, 2008-05-16 at 09:01 +0200, Sebastian Siewior wrote:
> > * Harvey Harrison | 2008-05-15 23:17:17 [-0700]:
> > 
> > >Make the michael_block macro a function and change the calling
> > >function to take a struct michael_mic_ctx * and the value for
> > >the initial xor with ctx->l.
> > >
> > >Also open-code xswap in its one use in michael_block.
> > Does this change have any performance impact?
> > The only user is wireless (I guess). Is it used frequently (sign every
> > packet for instance) or once in a while (in every re-keying)?
> 
> Every packet. I have no idea whether it has performance impact, very
> hard to even guess.
> 

Well, the code-size difference is significant (about 200 bytes smaller
on X86-32).  This macro is essentially an inline function that is pretty
large.

Attached find the objdump -d of the original and after the patch.  As it
is, this code isn't used anywhere that I can find as mac80211 has its
own implementation, I'm trying to see if there is much advantage in
keeping the private version over moving to the crypto one.

Harvey

View attachment "michael_mic.orig" of type "text/plain" (11197 bytes)

View attachment "michael_mic.patched" of type "text/plain" (7599 bytes)