linux-kernel - Re: [PATCH 3/3] Make jprobes a little safer for users

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Date:	Tue, 26 Jun 2007 16:03:58 +1000
From:	Michael Ellerman <michael@...erman.id.au>
To:	Christoph Hellwig <hch@....de>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...abs.org,
	linux-ia64@...r.kernel.org, linux-arch@...r.kernel.org,
	Andrew Morton <akpm@...l.org>, anil.s.keshavamurthy@...el.com,
	ananth@...ibm.com
Subject: Re: [PATCH 3/3] Make jprobes a little safer for users

On Tue, 2007-06-26 at 07:53 +0200, Christoph Hellwig wrote:
> On Tue, Jun 26, 2007 at 11:48:51AM +1000, Michael Ellerman wrote:
> > I realise jprobes are a razor-blades-included type of interface, but
> > that doesn't mean we can't try and make them safer to use. This guy I
> > know once wrote code like this:
> > 
> > struct jprobe jp = { .kp.symbol_name = "foo", .entry = "jprobe_foo" };
> > 
> > And then his kernel exploded. Oops.
> > 
> > This patch adds an arch hook, arch_deref_entry_point() (I don't like it either)
> > which takes the void * in a struct jprobe, and gives back the text address
> > that it represents.
> > 
> > We can then use that in register_jprobe() to check that the entry point
> > we're passed is actually in the kernel text, rather than just some random
> > value.
> 
> Please don't add more weak functions, they're utterly horrible for
> anyone trying to understand the code.  Otherwise this looks fine to me.

What do you recommend instead? #define ARCH_HAS_FOO_BAR ?

I don't see what's utterly horrible about them. The fact that they're
weak is fairly reasonable documentation that they're overridden
somewhere else. And grep/cscope/ctags will find both the weak and
non-weak versions for you?

cheers

-- 
Michael Ellerman
OzLabs, IBM Australia Development Lab

wwweb: http://michael.ellerman.id.au
phone: +61 2 6212 1183 (tie line 70 21183)

We do not inherit the earth from our ancestors,
we borrow it from our children. - S.M.A.R.T Person

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