linux-kernel - Re: [PATCH] ftrace: fix current

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, 28 Oct 2008 20:55:57 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Frédéric Weisbecker <fweisbec@...il.com>
cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] ftrace: fix current_tracer error return


On Wed, 29 Oct 2008, Fr?d?ric Weisbecker wrote:
> >
> > My test scripts automatically set or unset /proc/sys/kernel/ftrace_enabled
> >
> > I believe I wanted that to be default off when dynamic ftrace was not
> > active. Currently, it really shouldn't matter, because there's a check to
> > make sure that ftrace has a registered function before calling it.
> >
> > That was just my preference. But if you find it less confusing, then
> > having ftrace_enabled as default on even when dynamic ftrace is not
> > enabled, is fine with me.
> >
> > -- Steve
> >
> >
> 
> Thanks. I guess this bug was there for several days. But since I

But this was not a bug :-/

I believe I purposely set it that way. The bug was that you did not know 
that you could enable it with /proc/sys/kernel/ftrace_enabled ;-)


> always used dynamic ftrace, I've not
> seen it until yesterday. (BTW I didn't tested with dynamic since this
> patch). I had one other bug that made the set of
> function tracer blocking during the write on current_trace with
> dynamic ftrace. I will have a look on it.

Hmm, that could be a bug, but I do not know the details.

> 
> Actually one thing that makes me a bit confused is the use of these
> two vars: ftrace_enabled and ftrace_disabled.
> They are not used for the same purpose but their name suggest the same
> role.... :-)

Well, the code documents it pretty well:

/* ftrace_enabled is a method to turn ftrace on or off */
int ftrace_enabled __read_mostly;
static int last_ftrace_enabled;

/*
 * ftrace_disabled is set when an anomaly is discovered.
 * ftrace_disabled is much stronger than ftrace_enabled.
 */
static int ftrace_disabled __read_mostly;

-- Steve

--
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/