linux-kernel - Re: [RFC PATCH] dynamic debug - adding ring buffer storage support

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, 5 Jan 2010 07:05:37 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Frederic Weisbecker <fweisbec@...il.com>
Cc:	Jiri Olsa <jolsa@...hat.com>, Jason Baron <jbaron@...hat.com>,
	rostedt@...dmis.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] dynamic debug - adding ring buffer storage support


* Frederic Weisbecker <fweisbec@...il.com> wrote:

> On Mon, Dec 28, 2009 at 10:24:02AM +0100, Ingo Molnar wrote:
> > > that way you need to enable tracing as well... but thats ok I guess :)
> > > 
> > > I was investigating trace events for this, but did not find a way
> > > to put variable length argument inside... and I overlooked the
> > > trace_printk, I'll look on it and see how it fits, thanks
> > > 
> > > also having separate ring buffer makes the 'trace'/'trace_pipe' code
> > > really simple (suprissingly) compared to ftrace, and I thought
> > > on this place it could last for some time.. ;)
> > 
> > I think what we want is a unified channel of events, of which printk (and 
> > dynamic-printk) is one form. I.e. we should add printk events and 
> > dynamic-printk events as well, which would show up in /debug/tracing/events/ 
> > in a standard ftrace event form and would be accessible to tooling that way.
> > 
> > For printk a single event would be enough i suspect (we dont want a separate 
> > event for every printk), and for dynamic-printk we want to map the existing 
> > dyn-printk topologies into /debug/tracing/events, to preserve the distinctions 
> > and controls available there.
> > 
> > This way in the long run we'd have one unified facility.
> > 
> > 	Ingo
> 
> 
> That said, I sometimes dream about one event per printk.

Yeah - but it's only really useful if we could properly encode/extract the 
record format as well.

The one person's printk would become another person's programmable tracepoint.

> Too bad that would bloat the memory.

Should be optional of course, and then developers/distros pick instrumentation 
landscape winners/losers. To most people memory overhead is not a big issue, 
if the result is sufficiently useful.

	Ingo
--
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/