linux-kernel - Re: [PATCH] x86-64: memset optimization

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

Message-ID: <20070819010430.2c8c31fc@oldman.hemminger.net>
Date:	Sun, 19 Aug 2007 01:04:30 -0400
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	Andi Kleen <ak@...e.de>
Cc:	discuss@...-64.org, linux-kernel@...r.kernel.org, jh@...e.cz
Subject: Re: [PATCH] x86-64: memset optimization

On Sat, 18 Aug 2007 20:55:11 +0200
Andi Kleen <ak@...e.de> wrote:

> 
> > The problem is that on x86-64 you are overriding memset() 
> 
> I don't.  You must be looking at old source
> 
> asm-x86_64/string.h 2.6.23rc3:
> 
> #define __HAVE_ARCH_MEMSET
> void *memset(void *s, int c, size_t n);
> 
> I wanted to do the same on i386 too, but there were some minor obstacles.
> The problem is that the out of line fallback i386 memset is currently
> quite dumb and needs to be rewritten to expand the fill char on its
> own like the x86-64 version. Probably best would be just to port
> the x86-64 version. I just hadn't had time for that.
> 
> [Patches welcome, but if you do ask me for my old memset test harness]
> 
> -Andi

I am looking at current source, built with current (non-experimental) GCC
from Fedora Core 7. If I dissassemble ether_setup, which is

void ether_setup(struct net_device *dev)
{
...

	memset(dev->broadcast, 0xFF, ETH_ALEN);
}

I see a tail recursion (jmp) to memset which is the code in arch/x86_64/lib/memset.S

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/