linux-kernel - Re: replace "memset(...,0,PAGE_SIZE)" calls with "clear

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]

Date:	Sun, 31 Dec 2006 14:45:34 +0100
From:	Arjan van de Ven <arjan@...radead.org>
To:	Folkert van Heusden <folkert@...heusden.com>
Cc:	"Robert P. J. Day" <rpjday@...dspring.com>,
	Denis Vlasenko <vda.linux@...glemail.com>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: replace "memset(...,0,PAGE_SIZE)" calls with "clear_page()"?

On Sun, 2006-12-31 at 14:39 +0100, Folkert van Heusden wrote:
> > > i don't see how that can be true, given that most of the definitions
> > > of the clear_page() macro are simply invocations of memset().  see for
> > > yourself:
> > *MOST*. Not all.
> > For example an SSE version will at least assume 16 byte alignment, etc
> > etc.
> 
> What about an if (adress & 15) { memset } else { sse stuff }
> or is that too obvious? :-)


it's only one example. clear_page() working only on a full page is a
nice restriction that allows the implementation to be optimized (again
the x86 hardware that had a hardware page zeroer comes to mind, the hw
is only 4 years old or so... and future hw may have it again)

clear_page() is more restricted than memset(). And that's good, it
allows for a more focused implementation. Otherwise there'd be no reason
to HAVE a clear_page(), if it just was a memset wrapper entirely.



-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org

-
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/