linux-kernel - Re: [PATCH 01/22] ARM: add mechanism for late code patching

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Date:	Wed, 8 Aug 2012 17:05:17 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Nicolas Pitre <nicolas.pitre@...aro.org>
Cc:	Cyril Chemparathy <cyril@...com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Arnd Bergmann <arnd@...db.de>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>
Subject: Re: [PATCH 01/22] ARM: add mechanism for late code patching

On Wed, Aug 08, 2012 at 09:55:12AM -0400, Nicolas Pitre wrote:
> On Wed, 8 Aug 2012, Cyril Chemparathy wrote:
> > Neat macro magic.  Are you thinking that we build this in as a self test in
> > the code?
> 
> For such things, this is never a bad idea to have some test alongside 
> with the main code, especially if this is extended to more cases in the 
> future.  It is too easy to break it in subtle ways.
> 
> See arch/arm/kernel/kprobes-test*.c for a precedent.

Done correctly, it shouldn't be a problem, but I wouldn't say that
arch/arm/kernel/kprobes-test*.c is done correctly.  It's seen quite
a number of patching attempts since it was introduced for various
problems, and I've seen quite a number of builds fail for various
reasons in this file (none which I could be bothered to investigate.)

When the test code ends up causing more problems than the code it's
testing, something is definitely wrong.
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