linux-kernel - Re: [PATCH v0 04/71] itrace: Infrastructure for instruction flow tracing units

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:	Tue, 7 Jan 2014 09:38:03 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Jiri Olsa <jolsa@...hat.com>, Mike Galbraith <efault@....de>,
	Namhyung Kim <namhyung@...il.com>,
	Paul Mackerras <paulus@...ba.org>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v0 04/71] itrace: Infrastructure for instruction flow
 tracing units

On Mon, Jan 06, 2014 at 03:10:28PM -0800, Andi Kleen wrote:
> Peter Zijlstra <peterz@...radead.org> writes:
> > Also, do clarify the other points I asked about. Esp. the non
> > FREEZE_ON_PMI behaviour of the PT PMI is worrying me immensely.
> 
> The only reason for hardware freeze is when you have a few entries (like
> with LBRs) so the interrupt entry code could overwhelm it.
> 
> But PT is not small, it's gigantic: even with the smallest buffer you
> have many thousands of entries.
> 
> So you will get a few branches in the interrupt entry, but it's not a problem
> because everything you really wanted to trace is still there.
> 
> Eventually the handler disables PT, so there's no risk of racing with
> the update or anything like that.
> 
> Did I miss anything?

Yes; go read this:

 lkml.kernel.org/r/20131219125205.GT3694@...ns.programming.kicks-ass.net
--
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/