linux-kernel - Re: [PATCH 7/8] i386: bitops: Kill needless usage of __asm__ __volatile_

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: <Pine.LNX.4.64.0707232316440.22796@cselinux1.cse.iitk.ac.in>
Date:	Mon, 23 Jul 2007 23:37:51 +0530 (IST)
From:	Satyam Sharma <ssatyam@....iitk.ac.in>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Howells <dhowells@...hat.com>,
	Nick Piggin <nickpiggin@...oo.com.au>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 7/8] i386: bitops: Kill needless usage of __asm__
 __volatile__

On Mon, 23 Jul 2007, Jeremy Fitzhardinge wrote:

> I'm not quite sure what your point is.

Could be a case of terminology confusion ...

> The paragraph you quoted is
> pretty explicit in saying that volatile doesn't prevent an "asm
> volatile" from being interspersed with other code, and the example just
> before that is explicit in talking about how to use dependencies to
> control the ordering of asm volatiles with respect to surrounding code.

Yes, that was the (2).

> In fact nothing in that section precludes asm volatiles from being
> reordered with respect to each other either; you just have to make sure
> your dependency constraints are all correct.

The (3) as I had originally written / meant was that multiple
instructions in a volatile asm would not get _individually_
interspersed with the rest of the code i.e. be emitted out
_consecutively_. I don't think we need any such guarantees for
the non-atomic variants of those operations, so it's good to
let the compiler have a free hand with what it wants to do,
and optimize/combine multiple bitops as necessary / possible,
which was the original intention.

Satyam
-
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/