linux-kernel - Re: x86: A fast way to check capabilities of the current cpu

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: <AANLkTin=GXnLuDZncSL9rWKh5teCQP=3iQB-Rz8zxsnk@mail.gmail.com>
Date:	Wed, 15 Dec 2010 22:48:33 +0100
From:	Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux.com>, Tejun Heo <tj@...nel.org>,
	Pekka Enbeerg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org,
	Eric Dumazet <eric.dumazet@...il.com>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: x86: A fast way to check capabilities of the current cpu

On Wed, Dec 15, 2010 at 10:39 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 12/15/2010 01:30 PM, Miguel Ojeda wrote:
>>
>> In this case it this_cpu_*_test_bit() return an int, but they act as a
>> bool and are used in if()s; where is the catch?
>>
>
> If they aren't, and are stored in a variable for whatever reason, then
> the || form will generate additional instructions to booleanize the
> value for no good reason.

Thanks! I suppose that is the 't' of being "a fast way" ;-)

>
>        -hpa
>
--
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/