linux-kernel - Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64()

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:	Thu, 15 Apr 2010 09:48:12 +0100
From:	David Howells <dhowells@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	dhowells@...hat.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Matthew Wilcox <matthew@....cx>,
	Ralf Baechle <ralf@...ux-mips.org>, mingo@...e.hu,
	tglx@...utronix.de, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64()

Avi Kivity <avi@...hat.com> wrote:

> Even if Intel processors behave that way, other processors (real and
> emulated) use those manuals as a specification.  Emulated processors are
> unlikely to touch an undefined register, but real processors may.
> 
> (qemu tcg appears not to touch the output)

Possibly because the AMD64 spec specifies that the destination will be
unchanged if the source was 0.

David
--
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/