linux-kernel - Re: [PATCH 4/5] perf record: mmap output file

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:	Wed, 13 Nov 2013 12:34:39 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	David Ahern <dsahern@...il.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	linux-kernel@...r.kernel.org, jolsa@...hat.com,
	Frederic Weisbecker <fweisbec@...il.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Mike Galbraith <efault@....de>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 4/5] perf record: mmap output file - v5

On Tue, Nov 12, 2013 at 10:11:21PM +0100, Ingo Molnar wrote:
> 
> * David Ahern <dsahern@...il.com> wrote:
> 
> > > Dunno.. it _should_ all work. Try it and see what it does.. Once the 
> > > events are bigger than a page things might get 'interesting' though.
> 
> Which could be the case with call-graph recording, right?

Not typically, I think we're limiting call graphs to 127 u64, which is
~1k. Maybe you can blow the single page if you also do a large
top-of-stack copy for dwarf/unwind nonsense.

> > one option here is not allow page faults and system wide system calls. 
> > system wide tracing needs mmap; page faults for a task can use write(). 
> > I left that option in case something like this came up.
> 
> So maybe splice() sounds like the right long term solution after all? :-/

Right until you put a tracepoint (kprobe) somewhere in whatever function
is used to transfer a single page into/from a splice pipe.

You can always screw yourself over using this stuff, no exceptions.
--
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/