linux-kernel - Re: [RFT] Port 0x80 I/O speed

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] [day] [month] [year] [list]

Date:	Wed, 12 Dec 2007 15:48:01 +0100
From:	Rene Herman <rene.herman@...access.nl>
To:	linux@...izon.com
CC:	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [RFT] Port 0x80 I/O speed

On 12-12-07 12:20, linux@...izon.com wrote:

> Here are a variety of machines:

Thanks much for all! Collecting all data now...

> With -O2, the cycle counts come out (before division) as
> out: 0xFFFFFFFFFFEA6F4F
> in:  0xFFFFFFFFFCE68BB6
> I think the "A" constraint doesn't work quite the same in
> 64-bit code.  The compiler seems to be using %rdx rather than
> %edx:%eax.

Yes indeed, that tripped me up. Have been using the "=A" locally for a while 
for similar timing tests. Will use a manual "=a" (lo), "=d" (hi) I guess for 
amd64 compatibility from now on.

If I'd care deeply I'd probably categorize this as a backwards compatibility 
bug in GCC though. Things were probably never guaranteed but they certainly 
worked that way...

Rene.
--
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/