linux-kernel - Re: [patch 1/2] F00F bug fixup for i386

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: <20070714072239.GA5822@martell.zuzino.mipt.ru>
Date:	Sat, 14 Jul 2007 11:22:39 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [patch 1/2] F00F bug fixup for i386 - use immediate values

On Fri, Jul 13, 2007 at 09:26:43PM -0400, Mathieu Desnoyers wrote:
> Use the faster immediate values for F00F bug handling in do_page_fault.

> --- linux-2.6-lttng.orig/arch/i386/mm/fault.c
> +++ linux-2.6-lttng/arch/i386/mm/fault.c
> @@ -492,7 +493,7 @@
>  	/*
>  	 * Pentium F0 0F C7 C8 bug workaround.
>  	 */
> -	if (boot_cpu_data.f00f_bug) {
> +	immediate_if (&f00f_bug_fix) {

This code is not called during normal pagefaults and even during invalid
userspace accesses.

Out of curiosity, I inserted printk() at this place to see where I was
wrong. I got only two hits:

	Checking if this processor honours the WP bit even in supervisor mode... do_page_fault:
	Freeing unused kernel memory: 116k freed
	do_page_fault:

Resume: nobody gives a fuck about performance of this particular if,
	so conversion it totally pointless.

-
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/