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

From: Michael Ellerman
Date: Mon Jun 25 2007 - 22:07:00 EST


On Mon, 2007-06-25 at 19:00 -0700, Andrew Morton wrote:
> On Tue, 26 Jun 2007 11:48:51 +1000 (EST) Michael Ellerman <michael@xxxxxxxxxxxxxx> 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.
> >
> > Signed-off-by: Michael Ellerman <michael@xxxxxxxxxxxxxx>
> > ---
> > arch/ia64/kernel/kprobes.c | 7 ++++++-
> > arch/powerpc/kernel/kprobes.c | 11 ++++++++---
> > kernel/kprobes.c | 9 +++++++++
>
> We're missing a declaration of arch_deref_entry_point() in some header file?

Yeah I guess. It's declared weak in kernel/kprobes.c, but there should
be a definition somewhere to make sure the three versions don't get out
of sync. I'll send a patch.

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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