linux-kernel - Re: [PATCH 6/8] i386: bitops: Don't mark memory as clobbered unnecessarily

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: <alpine.LFD.0.999.0707251819160.3442@woody.linux-foundation.org>
Date:	Wed, 25 Jul 2007 18:22:20 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Trent Piepho <xyzzy@...akeasy.org>
cc:	Nick Piggin <nickpiggin@...oo.com.au>,
	Satyam Sharma <ssatyam@....iitk.ac.in>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Howells <dhowells@...hat.com>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 6/8] i386: bitops: Don't mark memory as clobbered
 unnecessarily



On Wed, 25 Jul 2007, Linus Torvalds wrote:
> 
> Hmm. I really think you should take this up with the gcc people. That 
> looks like a gcc bug - because there really is nothing that guarantees 
> that the asm doesn't change the array that "x" points to, and the asm 
> clearly talks about clobbering memory.

Actually, I take that back. I think gcc does the right thing, and yes, 
it's explained by the memory clobber being just a blind "write to memory" 
rather than read memory. My bad.

It does leave us with very few ways of saying that an asm can *read* 
memory, and so it might be good to have it clarified that "volatile" 
implies that (at least with the memory clobber).

Your examples are good, I think.

		Linus
-
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/