linux-kernel - Re: oprofile and ARM A9 hardware counter

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: <CACVXFVOygObWqPMLjg6uOB6inBkvvUjsQncNW0fbmpa4Xspw0Q@mail.gmail.com>
Date:	Fri, 17 Feb 2012 00:37:35 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Will Deacon <will.deacon@....com>,
	"eranian@...il.com" <eranian@...il.com>,
	"Shilimkar, Santosh" <santosh.shilimkar@...com>,
	David Long <dave.long@...aro.org>,
	"b-cousson@...com" <b-cousson@...com>,
	"mans@...sr.com" <mans@...sr.com>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: oprofile and ARM A9 hardware counter

On Fri, Feb 17, 2012 at 12:19 AM, Peter Zijlstra <a.p.zijlstra@...llo.nl> wrote:
> On Fri, 2012-02-17 at 00:12 +0800, Ming Lei wrote:
>> is triggered: u64 delta = 100 -  1000000 = 18446744073708551716.
>
> on x86 we do:
>
>  int shift = 64 - x86_pmu.cntval_bits;
>  s64 delta;
>
>  delta = (new_raw_count << shift) - (prev_raw_count << shift);
>  delta >>= shift;
>
> This deals with short overflows (on x86 the registers are typically 40
> or 48 bits wide). If the arm register is 32 you can of course also get
> there with some u32 casts.

Good idea, but it may not work if new_raw_count is bigger than prev_raw_count.

thanks
--
Ming Lei
--
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/