linux-kernel - Re: perf_counters: page fault trace record

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] [day] [month] [year] [list]

Message-ID: <4A36B15E.80806@linux.vnet.ibm.com>
Date:	Mon, 15 Jun 2009 13:38:54 -0700
From:	Corey Ashford <cjashfor@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Paul Mackerras <paulus@...ba.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: perf_counters: page fault trace record

Ingo Molnar wrote:
> * Paul Mackerras <paulus@...ba.org> wrote:
> 
>> Corey Ashford writes:
>>
>>> Paul Mackerras wrote:
>>>> Can't you do what you need just using a page fault software 
>>>> counter with sample_type = PERF_SAMPLE_IP | PERF_SAMPLE_ADDR 
>>>> and sample_period = 1?
>>> I thought about that, but I was under the (incorrect?) 
>>> impression that on Power, the PERF_SAMPLE_ADDR would be set by 
>>> the value of the SDAR register, which wouldn't be correct for 
>>> the case of a page fault.
>> No, the PERF_SAMPLE_ADDR value only comes from SDAR for a hardware 
>> counter overflow event.  For the page-fault software counter the 
>> PERF_SAMPLE_ADDR value will always be the faulting address.
> 
> Corey, could you please add support for it in 'perf'? We dont want 
> such sw-counter features to be in the kernel code without matching 
> support in tools/perf/.
> 
> While user data symbols wont be resolved, if we have a 
> --target-address switch in perf record we could see the faulting 
> frequency (and the fault coverage - and ordering as well) of shared 
> libraries, in perf report and perf annotate.
> 
> This would be a very useful facility.
> 
> Thanks,
> 
> 	Ingo

I'll see what I can do.  This will be my first time modifying perf, so expect 
that I won't do things the way you prefer the first couple of go-arounds :)

Regards,

- Corey


--
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/