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Subject: Re: [PATCH 1/2] tracing: Prevent unloadable modules from using
 trace_bprintk()
From: Steven Rostedt <rostedt@goodmis.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>
In-Reply-To: <20101021034255.GG5387@nowhere>
References: <20101021024233.530237054@goodmis.org>
	 <20101021024304.827826848@goodmis.org>  <20101021034255.GG5387@nowhere>
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Date: Wed, 20 Oct 2010 23:47:56 -0400
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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

-- Steve