linux-kernel - Re: [PATCH 06/31] perf, kvm: Support the intx/intx_cp modifiers in KVM arch perfmon emulation

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: <506C3583.4040506@redhat.com>
Date:	Wed, 03 Oct 2012 14:54:27 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Andi Kleen <ak@...ux.intel.com>
CC:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	acme@...hat.com, x86@...r.kernel.org, eranian@...gle.com,
	jolsa@...hat.com, a.p.zijlstra@...llo.nl
Subject: Re: [PATCH 06/31] perf, kvm: Support the intx/intx_cp modifiers in
 KVM arch perfmon emulation

On 10/03/2012 02:11 PM, Andi Kleen wrote:
>> > -			eventsel & ARCH_PERFMON_EVENTSEL_INT);
>> > +			eventsel & ARCH_PERFMON_EVENTSEL_INT,
>> > +			!!(eventsel & HSW_INTX),
>> > +			!!(eventsel & HSW_INTX_CHECKPOINTED));
>> >  }
>> >  
>> 
>> Those !! are !necessary, since the formal argument is a bool.
> 
> bool is 1 or 0, x & y with y > 1 is not 1 or 0.
> iirc assigning > 1 to bool is undefined
> 
> So I think they are necessary.

Conversion to bool coerces the value to 0 or 1.

_Bool ret(int x) { return x & 0x10000; }
  20:	81 e7 00 00 01 00    	and    $0x10000,%edi
  26:	0f 95 c0             	setne  %al
  29:	c3                   	retq


-- 
error compiling committee.c: too many arguments to function
--
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/