linux-kernel - Re: [PATCH] kprobes: add kprobe_is_function

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Message-ID: <alpine.LNX.2.00.1410220800040.22681@pobox.suse.cz>
Date:	Wed, 22 Oct 2014 08:02:23 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
cc:	Anil S Keshavamurthy <anil.s.keshavamurthy@...el.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	linux-kernel@...r.kernel.org, Josh Poimboeuf <jpoimboe@...hat.com>,
	Seth Jennings <sjenning@...hat.com>
Subject: Re: [PATCH] kprobes: add kprobe_is_function_probed()

On Wed, 22 Oct 2014, Masami Hiramatsu wrote:

> > Add a function that allows external users (such as live patching 
> > mechanisms) to check whether a given function (identified by symbol name) 
> > has a kprobe installed in it.
> 
> Actually, we've already exported the list of kprobes with probe points
> (symbols) via debugfs. Please check /sys/kernel/debug/kprobes/list :)

Yes, I know, and kprobe_is_function_probed() is performing very similar 
thing that show_kprobe_addr() is doing.
But we'd like to be able to check this from within a kernel module (the 
patch module) and issue WARN().

Otherwise we'll need to have a machinery in userspace before insmod which 
will look up the functions in the module and compare them to the 
debufs-provided interface.

Also, I don't think we want to be dependent on debugfs being mounted and 
discoverable, etc ...

Thanks Masami,

-- 
Jiri Kosina
SUSE Labs
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