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Date: Thu, 21 Oct 2010 05:54:46 +0200
From: Frederic Weisbecker <fweisbec@gmail.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 1/2] tracing: Prevent unloadable modules from using
	trace_bprintk()
Message-ID: <20101021035444.GH5387@nowhere>
References: <20101021024233.530237054@goodmis.org> <20101021024304.827826848@goodmis.org> <20101021034255.GG5387@nowhere> <1287632876.16971.561.camel@gandalf.stny.rr.com>
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On Wed, Oct 20, 2010 at 11:47:56PM -0400, Steven Rostedt wrote:
> On Thu, 2010-10-21 at 05:42 +0200, Frederic Weisbecker wrote:
> 
> > > +/*
> > > + * Module code must not use trace_bprintk, because if it is unloaded
> > > + * then we leave a pointer back to the module code inside
> > > + * the ring buffer, and then reading the ring buffer may cause a bug.
> > > + *
> > > + * We do allow for modules to use it if the kernel does not allow
> > > + * unloading of modules, and MODVERSIONS is set (to make sure kernel
> > > + * and module are the same). If you load modules without MODVERSIONS
> > > + * set, then you deserve what you get.
> > > + */
> > > +#if defined(MODULE) &&							\
> > 
> > 
> > 
> > Did you mean CONFIG_MODULE may be?
> 
> Nope, then the a kernel that allows modules wont use it. I do mean
> "MODULE", as in defined by the Makefile:
> 
> KBUILD_AFLAGS_MODULE  := -DMODULE
> KBUILD_CFLAGS_MODULE  := -DMODULE


Ah ok.

Thanks.